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• Heligmosomoides polygyrus secretes apyrases homologous to soluble calcium-activated nucleotidases. • Apyrases hydrolyse nucleoside triphosphates and diphosphates. • Expression is restricted to adults and L4s. • Vaccination with recombinant apyrases generates partial protection against infection. Apyrases are a recurrent feature of secretomes from numerous species of parasitic nematodes. Here we characterise the five apyrases secreted by Heligmosomoides polygyrus , a natural parasite of mice and a widely used laboratory model for intestinal nematode infection. All five enzymes are closely related to soluble calcium-activated nucleotidases described in a variety of organisms, and distinct from the CD39 family of ecto-nucleotidases. Expression is maximal in adult worms and restricted to adults and L4s. Recombinant apyrases were produced and purified from Pichia pastoris. The five enzymes showed very similar biochemical properties, with strict calcium dependence and a broad substrate specificity, catalysing the hydrolysis of all nucleoside tri- and diphosphates, with no activity against nucleoside monophosphates. Natural infection of mice provoked very low antibodies to any enzyme, but immunisation with an apyrase cocktail showed partial protection against reinfection, with reduced egg output and parasite recovery. The most likely role for nematode secreted apyrases is hydrolysis of extracellular ATP, which acts as an alarmin for cellular release of IL-33 and initiation of type 2 immunity. [ABSTRACT FROM AUTHOR]

Abstract The incidence of papillary thyroid carcinoma (PTC) has been increasing, which raised the interest in its molecular pathways. Although the high expression of ecto-5′-nucleotidase (NT5E) gene expression and NT5E enzymatic activity in several types of cancer is associated with tumor progression, its role in PTC remains unknown. Here, we investigated the AMP hydrolysis in human normal thyroid cells and PTC cells, in primary culture, and the association of NT5E expression with clinical aspects of PTC patients. AMPase activity was higher in thyroid cells isolated from PTC, as compared to normal thyroid (P = 0.0063). Significant correlation was observed between AMPase activity and NT5E levels in primary thyroid cell cultures (r = 0.655, P = 0.029). NT5E expression was higher in PTC than in the adjacent non-malignant thyroid tissue (P = 0.0065) and were positively associated with metastatic lymph nodes (P = 0.0007), risk of recurrence (P = 0.0033), tumor size (P = 0.049), and nodular hyperplasia in the adjacent thyroid parenchyma, when compared to normal thyroid or lymphocytic thyroiditis (P = 0.0146). After adjusting for potential confounders, the malignant/non-malignant paired expression ratio of NT5E mRNA was independently associated with metastatic lymph nodes (P = 0.0005), and tumor size (P=0.0005). In addition, the analysis of PTC described in the TCGA database also showed an association between higher expression of NT5E and metastatic lymph nodes, and tumor microinvasion. These results support the hypothesis that NT5E have a role in PTC microenvironment and might be a potential target for PTC therapy. Highlights • Ecto-5′-nucleotidase (NT5E/CD73) activity are up regulate in thyroid cells from papillary thyroid cancer. • Tumor size and lymph nodes metastasis in PTC were associated with upregulation of NT5E/CD73. • The TCGA dataset showed an association between higher levels of NT5E/CD73 and tumor microinvasion. • These data suggest NT5E/CD73 as a potential utility as prognostic marker. [ABSTRACT FROM AUTHOR]

Abstract Prenatal alcohol exposure causes alterations to the brain and can lead to numerous cognitive and behavioral outcomes. Long-lasting effects of early ethanol exposure have been registered in glutamatergic and dopaminergic systems. The purinergic system has been registered as an additional target of ethanol exposure. The objective of this research was to evaluate if the ecto‑5′‑nucleotidase and adenosine deaminase activities and gene expression of adult zebrafish exposed to 1% ethanol during early development could be part of the long-lasting targets of ethanol. Zebrafish embryos were exposed to 1% ethanol in two distinct developmental phases: gastrula/segmentation (5–24 h post-fertilization) or pharyngula (24–48 h post-fertilization). At the end of three months, after checking for morphological outcomes, the evaluation of enzymatic activity and gene expression was performed. Exposure to ethanol did not promote gross morphological defects; however, a significant decrease in the body length was observed (17% in the gastrula and 22% in the pharyngula stage, p < 0.0001). Ethanol exposure during the gastrula/segmentation stage promoted an increase in ecto‑5′‑nucleotidase activity (39.5%) when compared to the control/saline group (p < 0.0001). The ecto‑5′‑nucleotidase gene expression and the deamination of adenosine exerted by ecto and cytosolic adenosine deaminase were not affected by exposure to ethanol in both developmental stages. HPLC experiments did not identify differences in adenosine concentration on the whole encephala of adult animals exposed to ethanol during the gastrula stage or on control animals (p > 0.05). Although the mechanism underlying these findings requires further investigation, these results indicate that ethanol exposure during restricted periods of brain development can have long-term consequences on ecto‑5′‑nucleotidase activity, which could have an impact on subtle sequels of ethanol early exposure. Highlights • Ethanol exposure during early development increases adult AMP degradation. • Ecto‑5′‑nucleotidase increase is independent of gene expression. • Adenosine deaminase is not affected by ethanol exposure [ABSTRACT FROM AUTHOR]

This study investigated the effect of eugenol on arginase, nucleotidase and adenosine deaminase activities in platelets of carrageenan-induced arthritic rat model to explain a possible anti-arthritic mechanism of eugenol. Fifty adult female rats (140–250 g) were divided into ten (10) groups (n = 5). Group I received oral administration of corn oil, group II received 2.50 mg/kg of eugenol, group III and IV rats received oral administration of 5.0 and 10.0 mg/kg of eugenol respectively, group V received 0.20 mg/kg of dexamethasone orally, group VI rats was injected with 1% carrageenan (arthritic rats) and received saline solution orally (arthritic control rat group), group VII, VIII and IX: arthritic rats received 2.50, 5.0 or 10 mg/kg of eugenol orally respectively, group X: arthritic rats was administered with 0.20 mg/kg of dexamethasone orally. The animals were treated for 21 days, thereafter, tibiofemoral histological examination, thiobabituric acid reactive substances level, arginase, nucleoside triphosphate diphosphohydrolase, 5´-nucleotidase and adenosine deaminase activities were assessed. Tibiofemoral histological examination result showed that infiltration of inflammatory cells was significantly decreased with an increase in eugenol dose. Activities of arginase, adenosine triphosphate and adenosine monophosphate hydrolyses were significantly decreased while adenosine diphosphate hydrolysis and adenosine deaminase activities were significantly increased in arthritic rat groups administered with different doses of eugenol. Therefore, eugenol might be a natural complement and alternative promising anti-arthritic agent. These possible anti-arthritic mechanisms may be partly through the modulation of arginase and adenosine nucleotides hydrolyzing enzyme activities as well as the antioxidative action of eugenol. [ABSTRACT FROM AUTHOR]

Abstract There is growing evidence that uridine may act as an endogenous neuromodulator with a potential signaling role in the central nervous system in addition to its function in pyrimidine metabolism. We previously found that acute morphine treatment significantly increased uridine release in the dorsal striatum of mice, indicating that uridine may contribute to morphine-induced neurobehavioral changes. In the present study, we analyzed the mechanism involved in morphine-induced uridine release and the role of uridine in morphine-induced neurobehavioral changes. Uridine release in the dorsal striatum of mice was assessed by in vivo microdialysis coupled with high performance liquid chromatography (HPLC) after morphine treatment. Western blotting and immunofluorescence were used to evaluate the expression of uridine-related proteins. Morphine-induced neurobehavioral changes were assessed by locomotor activity, behavioral sensitization and conditioned place preference (CPP) test. The expression of NT5E, an extracellular enzyme involved in formation of nucleosides, including uridine, was specifically knocked down in the dorsal striatum of mice using adeno-associated virus (AAV)-mediated short hairpin RNA (shRNA). The results indicated that both acute and chronic morphine administration significantly increased uridine release in the dorsal striatum, and this was associated with upregulation of NT5E but not other uridine-related proteins. Inhibition of NT5E with APCP or shRNA markedly inhibited morphine-induced uridine release in the dorsal striatum and related neurobehavioral changes, including hyperlocomotor activity, behavioral sensitization and CPP. Our data give a better understanding of the contribution of NT5E to morphine-induced uridine release and neurobehavioral changes, and identify NT5E as a potential target for treating morphine abuse. Highlights • Morphine administration increased uridine release in the dorsal striatum. • Upregulation of NT5E was responsible for morphine-induced uridine release. • Inhibition of NT5E inhibited morphine-induced uridine release. • Inhibition of NT5E inhibited morphine-induced neurobehavioral changes. [ABSTRACT FROM AUTHOR]

Abstract P2Y receptors (P2YRs) are a family of G protein-coupled receptors activated by extracellular nucleotides. Physiological P2YR agonists include purine and pyrimidine nucleoside di- and triphosphates, such as ATP, ADP, UTP, UDP, nucleotide sugars, and dinucleotides. Eight subtypes exist, P2Y 1 , P2Y 2 , P2Y 4 , P2Y 6 , P2Y 11 , P2Y 12 , P2Y 13 , and P2Y 14 , which represent current or potential future drug targets. Here we provide a comprehensive overview of ligands for the subgroup of the P2YR family that is activated by uracil nucleotides: P2Y 2 (UTP, also ATP and dinucleotides), P2Y 4 (UTP), P2Y 6 (UDP), and P2Y 14 (UDP, UDP-glucose, UDP-galactose). The physiological agonists are metabolically unstable due to their fast hydrolysis by ectonucleotidases. A number of agonists with increased potency, subtype-selectivity and/or enzymatic stability have been developed in recent years. Useful P2Y 2 R agonists include MRS2698 (6 - 01 , highly selective) and PSB-1114 (6 - 05 , increased metabolic stability). A potent and selective P2Y 2 R antagonist is AR-C118925 (10 - 01). For studies of the P2Y 4 R, MRS4062 (3 - 15) may be used as a selective agonist, while PSB-16133 (10 - 06) is a selective antagonist. Several potent P2Y 6 R agonists have been developed including 5-methoxyuridine 5′- O -((R p)α-boranodiphosphate) (6 - 12), PSB-0474 (3 - 11), and MRS2693 (3 - 26). The isocyanate MRS2578 (10 - 08) is used as a selective P2Y 6 R antagonist, although its reactivity and low water-solubility are limiting. With MRS2905 (6 - 08), a potent and metabolically stable P2Y 14 R agonist is available, while PPTN (10 - 14) represents a potent and selective P2Y 14 R antagonist. The radioligand [3H]UDP can be used to label P2Y 14 Rs. In addition, several fluorescent probes have been developed. Uracil nucleotide-activated P2YRs show great potential as drug targets, especially in inflammation, cancer, cardiovascular and neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Abstract The ecto-5′-nucleotidase CD73 has emerged as an important drug target in oncoimmunology as well as in other diseases. We describe new ADP analogues as CD73 inhibitors based on the replacement of the adenosine moiety, in the reference inhibitor APCP, by purine nucleoside analogues. Compounds were assessed for CD73 inhibition both on purified recombinant protein and on CD73-expressing cancer cells. The clofarabine-containing compound (2) was shown to be more potent than APCP with IC50 values of 0.18 μM (vs. 3.8 μM) on purified protein and 0.24 μM (vs. 23.6 μM) on CD73 expressed on cells. This work gives additional insights into structure-activity relationship of substrate-analogues as CD73 inhibitors. Graphical abstract Image 1 Highlights • CD73 is involved in production of extracellular adenosine. • Adenosine stimulates tumor growth through immunosuppression. • New CD73 inhibitors are required for cancer treatment. [ABSTRACT FROM AUTHOR]

Abstract Background The calcific aortic valve disease (CAVD) is a common heart pathology that involves inflammation, fibrosis, and calcification of aortic valve leaflets. All these processes could be affected by changes in the extracellular purinergic signaling that depend on the activity of ectonucleotidases, mainly ectonucleoside triphosphate diphosphohydrolase 1 (CD39, eNTPD1) and ecto-5’nucleotidase (CD73, e5NT). Objective and methods We investigated the localization of CD39 and CD73 proteins in human noncalcified and calcified aortic valves using immunohistochemistry together with analysis of NTPDases and e5NT activities in aortic valve homogenates by analysis of substrate into product conversion by high-performance liquid chromatography. We also measured the rates of extracellular nucleotide catabolism on the surface of isolated cultured aortic valve endothelial (hAVECs) and interstitial cells (hAVICs) as well as characterized cellular CD39 and CD73 distribution. Results In noncalcified valves, CD39 and CD73 were expressed in both endothelial and interstitial cells, while in calcified valves, the expressions of CD39 and CD73 were significantly down-regulated with the exception of calcified regions where the expression of CD73 was maintained. This correlated with activities in valve homogenates. NTPDase was reduced by 35% and e5NT activity by 50% in calcified vs. noncalcified valve. CD39 and CD73 were present mainly in the cell membrane of hAVECs, but in hAVICs, these proteins were also present intracellularly. The rates of extracellular adenosine triphosphate and adenosine monophosphate hydrolysis in isolated hAVECs and hAVICs were comparable. Conclusion The presence of ectonucleotidases in valves and especially in aortic valve interstitial cells highlights important local role of purinergic signaling and metabolism. Changes in the local expression and hence the activity of CD39 and CD73 in calcified valves suggest their potential role in CAVD. Highlights • The expressions of CD39 and CD73 were significantly down-regulated in calcified valves. • Activity of NTPDase was reduced by 35%, while e5NT activity was reduced by 50% in calcified valve. • CD39 and CD73 were present mainly in the cell membrane of hAVECs. • In hAVICs, these proteins were also present intracellularly. • Results highlight possible role of purinergic signaling in valves calcification. [ABSTRACT FROM AUTHOR]

Highlights • We report the sensitivity and clinical utility of the anti-cN1A antibody test in sporadic inclusion body myositis (IBM). • This is a retrospective review of 40 patients with clinico-pathologically defined or clinically defined IBM. • The anti-cN1A antibody test has limited diagnostic utility in IBM. Abstract Sporadic inclusion body myositis (IBM) is the most common acquired myopathy affecting patients over age 50. The discovery of an autoantibody directed against a 43–44 kD protein (anti-cytosolic-5′-nucleotidase 1A or anti-cN1A) has provided support for the hypothesis of an immune-mediated pathogenesis. Previous studies have reported variable test sensitivity and specificity, and inconsistent results on the predictive value. In our cohort of 40 patients with clinico-pathologically or clinically defined IBM, we found the sensitivity of the anti-cN1A antibody test to be 50%. Comparing characteristics for test positive and test negative groups, we found that patients in our cohort testing positive for the anti-cN1A antibody were significantly more likely to be older than age 60 years at symptom onset. We found no positive association between anti-cN1A reactivity and other clinical, laboratory, and muscle histopathologic findings. Based on all clinical studies published to date including the present, the anti-cN1A antibody test shows high diagnostic specificity, moderate sensitivity, and a low predictive value in regards to age of onset, disease severity and other associated clinicopathological findings. [ABSTRACT FROM AUTHOR]

The Gram-negative bacterium Legionella pneumophila is one of the known opportunistic human pathogens with a gene coding for a zinc-dependent S1–P1 type nuclease. Bacterial zinc-dependent 3′-nucleases/nucleotidases are little characterized and not fully understood, including L. pneumophila nuclease 1 (Lpn1), in contrast to many eukaryotic representatives with in-depth studies available. To help explain the principle properties and role of these enzymes in intracellular prokaryotic pathogens we have designed and optimized a heterologous expression protocol utilizing E. coli together with an efficient purification procedure, and performed detailed characterization of the enzyme. Replacement of Ni 2+ ions by Zn 2+ ions in affinity purification proved to be a crucial step in the production of pure and stable protein. The production protocol provides protein with high yield, purity, stability, and solubility for structure-function studies. We show that highly thermostable Lpn1 is active mainly towards RNA and ssDNA, with pH optima 7.0 and 6.0, respectively, with low activity towards dsDNA; the enzyme features pronounced substrate inhibition. Bioinformatic and experimental analysis, together with computer modeling and electrostatics calculations point to an unusually high positive charge on the enzyme surface under optimal conditions for catalysis. The results help explain the catalytic properties of Lpn1 and its substrate inhibition. [ABSTRACT FROM AUTHOR]

Purine bases and nucleosides are produced by turnover of nucleotides and nucleic acids as well as from some cellular metabolic pathways. Adenosine released from the S -adenosyl-L-methionine cycle is linked to many methyltransferase reactions, such as the biosynthesis of caffeine and glycine betaine. Adenine is produced by the methionine cycles, which is related to other biosynthesis pathways, such those for the production of ethylene, nicotianamine and polyamines. These purine compounds are recycled for nucleotide biosynthesis by so-called “salvage pathways”. However, the salvage pathways are not merely supplementary routes for nucleotide biosynthesis, but have essential functions in many plant processes. In plants, the major salvage enzymes are adenine phosphoribosyltransferase (EC 2.4.2.7) and adenosine kinase (EC 2.7.1.20). AMP produced by these enzymes is converted to ATP and utilised as an energy source as well as for nucleic acid synthesis. Hypoxanthine, guanine, inosine and guanosine are salvaged to IMP and GMP by hypoxanthine/guanine phosphoribosyltransferase (EC 2.4.2.8) and inosine/guanosine kinase (EC 2.7.1.73). In contrast to de novo purine nucleotide biosynthesis, synthesis by the salvage pathways is extremely favourable, energetically, for cells. In addition, operation of the salvage pathway reduces the intracellular levels of purine bases and nucleosides which inhibit other metabolic reactions. The purine salvage enzymes also catalyse the respective formation of cytokinin ribotides, from cytokinin bases, and cytokinin ribosides. Since cytokinin bases are the active form of cytokinin hormones, these enzymes act to maintain homeostasis of cellular cytokinin bioactivity. This article summarises current knowledge of purine salvage pathways and their possible function in plants and purine salvage activities associated with various physiological phenomena are reviewed. [ABSTRACT FROM AUTHOR]

Snake venom is a variable phenotypic trait, whose plasticity and evolution are critical for effective antivenom production. A significant reduction of the number of snake donations to Butantan Institute (São Paulo, Brazil) occurred in recent years, and this fact may impair the production of the Brazilian Bothropic Reference Venom (BBRV). Nevertheless, in the last decades a high number of Bothrops jararaca specimens have been raised in captivity in the Laboratory of Herpetology of Butantan Institute. Considering these facts, we compared the biochemical and biological profiles of B. jararaca venom from captive specimens and BBRV in order to understand the potential effects of snake captivity upon the venom composition. Electrophoretic analysis and proteomic profiling revealed few differences in venom protein bands and some differentially abundant toxins. Comparison of enzymatic activities showed minor differences between the two venoms. Similar cross-reactivity recognition pattern of both venoms by the antibothropic antivenom produced by Butantan Institute was observed. Lethality and neutralization of lethality for B. jararaca venom from captive specimens and BBRV showed similar values. Considering these results we suggest that the inclusion of B. jararaca venom from captive specimens in the composition of BBRV would not interfere with the quality of this reference venom. Biological significance Snakebite envenomation is a neglected tropical pathology whose treatment is based on the use of specific antivenoms. Bothrops jararaca is responsible for the majority of snakebites in South and Southeastern Brazil. Its venom shows individual, sexual, and ontogenetic variability, however, the effect of animal captivity upon venom composition is unknown. Considering the reduced number of wild-caught snakes donated to Butantan Institute in the last decades, and the increased life expectancy of the snakes raised in captivity in the Laboratory of Herpetology, this work focused on the comparative profiling of B. jararaca venom from captive snakes and the Brazilian Bothropic Reference Venom (BBRV). BBRV is composed of venom obtained upon the first milking of wild-caught B. jararaca specimens, and used to assess the potency of all bothropic antivenoms produced by Brazilian suppliers. The use of proteomic strategies, added to biochemical and neutralization tests, allowed to conclude that, despite some subtle differences detected between these two venoms, venom from captive specimens could be used in the BBRV composition without affecting its quality in antivenom potency assays. [ABSTRACT FROM AUTHOR]

The hydrolysis of nucleoside 5′-monophosphates to the corresponding nucleosides and inorganic phosphate is catalysed by 5′-nucleotidases, thereby contributing to the control of endogenous nucleotide turnover and affecting the fate of exogenously delivered nucleotide- and nucleoside-derived therapeutics in cells. A recently identified nucleotidase cNIIIB shows preference towards 7-methylguanosine monophosphate (m 7 GMP) as a substrate, which suggests its potential involvement in mRNA degradation. However, the extent of biological functions and the significance of cNIIIB remains to be elucidated. Here, we synthesised a series of m 7 GMP analogues carrying a 1,2,3-triazole moiety at the 5′ position as the potential inhibitors of human cNIIIB. The compounds were synthesised by using the copper-catalysed azide-alkyne cycloaddition (CuAAC) between 5′-azido-5′-deoxy-7-methylguanosine and different phosphate or phosphonate derivatives carrying terminal alkyne. The analogues were evaluated as cNIIIB inhibitors using HPLC and malachite green assays, demonstrating that compound 1a , carrying a 1,2,3-triazoylphosphonate moiety, inhibits cNIIIB activity at micromolar concentrations (IC 50 87.8 ± 7.5 µM), while other analogues showed no activity. In addition, compound 1d was identified as an artifical substrate for Hs cNIIIB. Further characterization of inhibitor 1a revealed that it is poorly recognised by other m 7 G-binding proteins, eIF4E and DcpS, indicating its selectivity towards cNIIIB. The first inhibitor ( 1a ) and unnatural substrate ( 1d ) of cNIIIB, identified here, can be used as molecular probes for the elucidation of biological roles of cNIIIB, including the verification of its proposed function in mRNA metabolism. [ABSTRACT FROM AUTHOR]

Background Extracellular vesicles released by different cells have been isolated from diverse fluids including saliva. We previously reported that rat submandibular glands secrete nanovesicles that catalyze hydrolysis of ATP, ADP and AMP, which are actors of the purinergic signaling system along with adenosine. Extracellular nucleotides like ATP and adenosine are involved in the regulation of inflammatory processes and apoptosis. Histamine, a widely distributed biogenic amine, is involved in inflammatory response. Objective To test if activation of histamine receptors in rat submandibular gland promotes changes in the release of vesicles with nucleotidase activity that could modulate purinergic signaling. Methods Rat submandibular glands were incubated in the absence or presence of histamine and JNJ7777120, an antagonist for H 4 receptors. Extracellular vesicles were isolated from incubation media by differential centrifugation. Vesicular nucleotidase activity was measured following Pi release by 3 mM MgATP, MgADP or MgAMP. Results Histamine increased the release of vesicles with nucleotidase activity in a concentration dependent manner. JNJ7777120 significantly reduced this effect. Vesicular nucleotidases obtained in the absence or presence of histamine promoted Pi production from ATP, ADP and AMP. Conclusion The results show a relationship between histamine and the regulation of purinergic signaling, which could be important in the modulation of inflammatory processes. [ABSTRACT FROM AUTHOR]

Over the past few years, several preclinical studies have highlighted the value of CD73 (ecto-5′-nucleotidase) as a potential therapeutic target for cancer therapy. Indeed, the pharmacological blockade of CD73, via monoclonal antibodies or small molecules, has promise in counteracting cancer development, growth and spread. Synergistic combinations of anti-CD73 drugs with conventional cancer treatments (i.e., chemotherapy, radiation therapy, immunotherapy, targeted therapy) have increased therapeutic potential. In this review, we discuss the potential synergistic effects of CD73 blockers and conventional antineoplastic therapies in the treatment of cancer. [ABSTRACT FROM AUTHOR]

Ecto-5′-nucleotidase (CD73) generates adenosine, an osteoblast activator and key regulator of skeletal growth. It is unknown, however, if CD73 regulates osteogenic differentiation during fracture healing in adulthood, and in particular how CD73 activity regulates intramembranous bone repair in the elderly. Monocortical tibial defects were created in 46–52-week-old wild type (WT) and CD73 knock-out mice (CD73 −/− ) mice. Injury repair was analyzed at post-operative days 5, 7, 14 and 21 by micro-computed tomography (micro-CT), histomorphometry, proliferating cell nuclear antigen (PCNA) immunostaining, alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) histochemistry. Middle-aged CD73 knock-out mice exhibited delayed bone regeneration and significantly reduced bone matrix deposition detected by histomorphometry and micro-CT. Cell proliferation, ALP activity and osteoclast number were reduced in the CD73 −/− mice, suggesting a combined defect in bone formation and resorption due the absence of CD73 activity in this model of intramembranous bone repair. Results from this study demonstrate that osteoblast activation through CD73 activity is essential during bone repair in aging mice, and it may present a drugable target for future biomimetic therapeutic approaches that aim at enhancing bone formation in the elderly patients. [ABSTRACT FROM AUTHOR]

Examined in the present study, allopurinol are xanthine oxidase inhibitors for use in rat hearts in vivo dialysis technology and ventricular myocardial intersitial adenosine production can increase. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts and the tissue in the vicinity of the dialysis was perfused with Tyrode's solution containing adenosine 5'-monophosphate (AMP) through the dialysis probe at a rate of 1.0 ml/min to assess the activity of ecto-5'-nucleotidase. Allopurinol (10 μM) significantly increased the level of adenosine in rat heart dialysate (n=6, p<0.05), which was inhibited by chelerythrine, 10 μM, an antagonist of protein kinase C (PKC). Another free radical scavenger, coenzyme Q10 (CoQ10, 100 μM) or ascorbic acid (Vitamin C; 100 μM) also increased adenosine production. In addition, allopurinol enhanced the diacylglycerol (DAG; 50 μM)-induced also increases in adenosine production by 71.5±12.0% (n=6, P<0.05), to a level significantly (P<0.05) greater than the increase caused by DAG alone (33.0±10.6%). In the presence of allopurinol (10 μM), a marked elevation of AMP-primed dialysate adenosine in ischemia/reperfused rat hearts was observed. Free radical generation may suppress adenosine production via activation of PKC. The results suggest that oxidative stress may cause inactivation of nucleotidase, adenosine production in rat heart. [ABSTRACT FROM AUTHOR]

Leishmaniases are vector-borne diseases for which no vaccine exists. These diseases are caused by the Leishmania species complex. Activation of the CD8 + T cell is crucial for protection against intracellular pathogens, and peptide antigens are attractive strategies for the precise activation of CD8 + T in vaccine development against intracellular infections. The traditional approach to mine the epitopes is an arduous task. However, with the advent of immunoinformatics, in silico epitope prediction tools are available to expedite epitope identification. In this study, we employ different immunoinformatics tools to predict CD8 + T cell specific 9 mer epitopes presented by HLA-A*02 and HLA-B40 within the highly conserved 3′-ectonucleotidase of Leishmania donovani . We identify five promiscuous epitopes, which have no homologs in humans, theoretically cover 85% of the world's population and are highly conserved (100%) among Leishmania species. Presentation of selected peptides was confirmed by T2 cell line based HLA-stabilization assay, and three of them were found to be strong binders. The in vitro peptide stimulation of peripheral blood mononuclear cells (PBMC) from cured HLA-A02 + visceral leishmaniasis (VL) subjects produced significantly higher IFN-γ, IL-2 and IL-12 compared to no peptide control healthy subjects. Further, CD8 + cells from treated VL subjects produced significantly higher intracellular IFN-γ, lymphocyte proliferation and cytotoxic activity against selected peptides from the PBMCs of treated HLA-A02 + VL subjects. Thus, the CD8 + T cell specific epitopes shown in this study will speed up the development of polytope vaccines for leishmaniasis. [ABSTRACT FROM AUTHOR]

Aortic stenosis is known to involve inflammation and thrombosis. Changes in activity of extracellular enzyme - ecto-5′-nucleotidase (referred also as CD73) can alter inflammatory and thrombotic responses. This study aimed to evaluate the effect of CD73 deletion in mice on development of aortic valve dysfunction and to compare it to the effect of high-fat diet. Four groups of mice (normal-diet Wild Type (WT), high-fat diet WT, normal diet CD73 −/−, high-fat diet CD73 −/−) were maintained for 15 weeks followed by echocardiographic analysis of aortic valve function, measurement of aortic surface activities of nucleotide catabolism enzymes as well as alkaline phosphatase activity, mineral composition and histology of aortic valve leaflets. CD73 −/− knock out led to an increase in peak aortic flow (1.06 ± 0.26 m/s) compared to WT (0.79 ± 0.26 m/s) indicating obstruction. Highest values of peak aortic flow (1.26 ± 0.31 m/s) were observed in high-fat diet CD73 −/− mice. Histological analysis showed morphological changes in CD73 −/− including thickening and accumulation of dark deposits, proved to be melanin. Concentrations of Ca 2 + , Mg 2 + and PO 4 3 − in valve leaflets were elevated in CD73 −/− mice. Alkaline phosphatase (ALP) activity was enhanced after ATP treatment and reduced after adenosine treatment in aortas incubated in osteogenic medium. AMP hydrolysis in CD73 −/− was below 10% of WT. Activity of ecto-adenosine deaminase (eADA), responsible for adenosine deamination, in the CD73 −/− was 40% lower when compared to WT. Deletion of CD73 in mice leads to aortic valve dysfunction similar to that induced by high-fat diet suggesting important role of this surface protein in maintaining heart valve integrity. [ABSTRACT FROM AUTHOR]

Background and aims Mutations in the 5'-nucleotidase ecto (NT5E) gene that encodes CD73, a nucleotidase that converts AMP to adenosine, are linked to arterial calcification. However, the role of purinergic receptor signaling in the pathology of intimal calcification is not well understood. In this study, we examined whether extracellular nucleotides acting via P2Y 2 receptor (P2Y 2 R) modulate arterial intimal calcification, a condition highly correlated with cardiovascular morbidity. Methods Apolipoprotein E, P2Y 2 R double knockout mice ( ApoE − / − P2Y 2 R − / − ) were used to determine the effect of P2Y 2 R deficiency on vascular calcification in vivo . Vascular smooth muscle cells (VSMC) isolated from P2Y 2 R − / − mice grown in high phosphate medium were used to assess the role of P2Y 2 R in the conversion of VSMC into osteoblasts. Luciferase-reporter assays were used to assess the effect of P2Y 2 R on the transcriptional activity of Runx2. Results P2Y 2 R deficiency in ApoE − / − mice caused extensive intimal calcification despite a significant reduction in atherosclerosis and macrophage plaque content. The ectoenzyme apyrase that degrades nucleoside di- and triphosphates accelerated high phosphate-induced calcium deposition in cultured VSMC. Expression of P2Y 2 R inhibits calcification in vitro inhibited the osteoblastic trans -differentiation of VSMC. Mechanistically, expression of P2Y 2 R inhibited Runx2 transcriptional activation of an osteocalcin promoter driven luciferase reporter gene. Conclusions This study reveals a role for vascular P2Y 2 R as an inhibitor of arterial intimal calcification and provides a new mechanistic insight into the regulation of the osteoblastic trans -differentiation of SMC through P2Y 2 R-mediated Runx2 antagonism. Given that calcification of atherosclerotic lesions is a significant clinical problem, activating P2Y 2 R may be an effective therapeutic approach for treatment or prevention of vascular calcification. [ABSTRACT FROM AUTHOR]

Diseases related to thyroid hormones have been extensively studied because affect a large number of individuals, and these hormones participate in the regulation of the whole organism homeostasis. However, little is known about the involvement of purinergic signaling related to oxidative stress in hypothyroidism and possible therapeutic adjuncts for treatment of this disorder. Thus, the present study investigates the effects of quercetin on NTPDase, 5′-nucleotidase and adenosine deaminase activities, platelet aggregation and oxidative profile in platelets of rats with methimazole (MMI)-induced hypothyroidism. Methimazole at a concentration of 20 mg/100 mL was administered for 90 days. From the second month the animals received quercetin 10 or 25 mg/kg for 60 days. Results showed that: Ecto-5′-nucleotidase activity decreased in methimazole/water group and the treatment with quercetin 25 mg/kg decreased NTPDase, 5′-nucleotidase and adenosine deaminase activities. Moreover, platelet aggregation increased in methimazole/water group. Lipid peroxidation increased while superoxide dismutase and catalase activities decreased, but, interestingly, the treatment with quercetin reversed these changes. These results demonstrated that quercetin modulates adenine nucleotide hydrolysis decreasing the ADP formation and adenosine deamination. At the same time quercetin improves the oxidative profile, as well as reduces platelet aggregation, which together with the modulation in the nucleotides levels can contribute to the prevention of platelet disorders. [ABSTRACT FROM AUTHOR]

The present study investigated the protective effect of quercetin (Querc) on memory, anxiety-like behavior and impairment of ectonucleotidases and acetylcholinesterase (AChE) activities in brain of streptozotocin-induced diabetic rats (STZ-diabetes). The type 1 diabetes mellitus was induced by an intraperitoneal injection of 70 mg/kg of streptozotocin (STZ), diluted in 0.1 M sodium-citrate buffer (pH 4.5). Querc was dissolved in 25% ethanol and administered by gavage at the doses of 5, 25 and 50 mg/kg once a day during 40 days. The animals were distributed in eight groups of ten animals as follows: vehicle, Querc 5 mg/kg, Querc 25 mg/kg, Querc 50 mg/kg, diabetes, diabetes plus Querc 5 mg/kg, diabetes plus Querc 25 mg/kg and diabetes plus Querc 50 mg/kg. Querc was able to prevent the impairment of memory and the anxiogenic-like behavior induced by STZ-diabetes. In addition, Querc prevents the decrease in the NTPDase and increase in the adenosine deaminase (ADA) activities in SN from cerebral cortex of STZ-diabetes. STZ-diabetes increased the AChE activity in SN from cerebral cortex and hippocampus. Querc 50 mg/kg was more effective to prevent the increase in AChE activity in the brain of STZ-diabetes. Querc also prevented an increase in the malondialdehyde levels in all the brain structures. In conclusion, the present findings showed that Querc could prevent the impairment of the enzymes that regulate the purinergic and cholinergic extracellular signaling and improve the memory and anxiety-like behavior induced by STZ-diabetes. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate seric NTPDase and 5′nucleotidase activities of cattle naturally infected by Eurytrema coelomanticum , as well as to correlate them to histopathological lesions in the pancreas and the degree of parasitism. Blood samples and pancreas of 51 bovines were collected on a slaughterhouse in Southern Brazil: 33 from cattle naturally infected by E. coelomanticum (the Group A), and 18 from uninfected animals (the Group B). Infected animals showed an average of 532 parasites per pancreas. In the pancreatic histology, ducts displayed hyperplasia, stenosis, proliferation of fibrous tissue, and interstitial inflammatory infiltration of lymphocytes. The serum from infected animals showed an increase in NTPDase activity when ATP was used as substrate (P < 0.001). For the ADP substrate, there was no difference between groups regarding NTPDase activity (P = 0.37), as well as 5′-nucleotidase activity (P = 0.27). Correlating NTPDase activity (ATP substrate) with the degree of histopathological lesions (rho = 0.66, P < 0.001) and the parasitic load on the pancreas (rho = 0.65, P < 0.001), a positive correlation was observed. Similar results were found between the degree of histopathological lesions and NTPDase activity (ADP substrate; rho = 0.29, P = 0.03), and 5′nucleotidase activity (rho = 0.35, P = 0.01). Based on the results of NTPDase and 5′nucleotidase enzymes in cattle naturally infected by E. coleomanticum , it is possible to suggest that these enzymes are involved in the modulation of inflammation, and they can act as markers of inflammatory response. [ABSTRACT FROM AUTHOR]

JNJ-63623872 (formally known as VX-787; referred to here as JNJ872) is an orally bioavailable compound, which is in phase II clinical trials for the treatment of influenza A virus (IAV) infections. Here we show that JNJ872 inhibits at nanomolar concentrations the transcription of viral RNA in IAV-infected human macrophages by targeting a highly conserved site on the cap-snatching domain of influenza polymerase basic 2 protein (PB2). Furthermore, even lower concentrations of JNJ872 protected macrophages from IAV-mediated death when given in combination with 100 nM gemcitabine, which also attenuated transcription and replication of viral RNA. Importantly, treating human macrophages with JNJ872 allowed expression of many immune-related and other genes, involved in antiviral responses, such as indoleamine 2,3-dioxygenase 1 ( IDO ), and cytosolic 5'-nucleotidase 3A ( NT5C3A ). Moreover, our targeted metabolomics analysis indicate that treatment with JNJ782 did not interfere with metabolic responses to infection, which further supported our transcriptomics results. Thus, VX-737 alone or in combination with other drugs could be beneficial for treating IAV infected patients, because it would allow the development of antiviral responses and, thereby, protect individuals from current and future infections with closely related IAV strains. [ABSTRACT FROM AUTHOR]

Multiple immunosuppressive mechanisms impede anti-tumor immunity. Among them, the accumulation of extracellular adenosine is a potent and widespread strategy exploited by tumors to escape immunosurveillance through the activation of purinergic receptors. In the immune system, engagement of A2a and A2b adenosine receptors is a critical regulatory mechanism that protects tissues against excessive immune reactions. In tumors, this pathway is hijacked and hinders anti-tumor immunity, promoting cancer progression. Different groups have highlighted the therapeutic potential of blocking CD73-dependent adenosine-mediated immunosuppression to reinstate anti-tumor immunity. Phase clinical trials evaluating anti-CD73 antibodies and A2a receptor antagonists in cancer patients are currently ongoing. We here review the recent literature on the immunosuppressive effects of extracellular adenosine and discuss the development of adenosine inhibitors. [ABSTRACT FROM AUTHOR]

Schistosomiasis is caused by an intravascular parasite and linked to phenotypic changes in endothelial cells that favor inflammation. Endothelial cells express P2Y 1 receptors (P2Y 1 R), and their activation by ADP favors leukocyte adhesion to the endothelial monolayer. We aimed to evaluate the influence of schistosomiasis upon endothelial purinergic signaling-mediated leukocyte adhesion. Mesenteric endothelial cells and mononuclear cells from control and Schistosoma mansoni -infected mice were used in co-culture. P2Y 1 R levels were similar in both groups. Basal leukocyte adhesion was higher in the infected than in the control group; leukocyte adhesion increased after treatment with the P2Y 1 R agonist 2-MeSATP in both groups, though it only marginally increased in the infected group. Pre-incubation with the selective P2Y 1 R antagonist MRS2179 (0.3 μM) prevented the agonist effect. However, in the infected group it also reduced the basal leukocyte adhesion, suggesting endothelial cell pre-activation. The endothelial expressions of NTPDases 2 and 3 were significantly increased in the infected group, increasing extracellular ATP hydrolysis and ADP formation by endothelial cells. Therefore, mesenteric endothelial cells are primed by schistosomiasis to a pro-inflammatory phenotype characterized by an increased expression of NTPDases 2 and 3, favoring ADP accumulation and mononuclear cell adhesion, possibly contributing to mesenteric inflammation and schistosomiasis morbidity. [ABSTRACT FROM AUTHOR]

A facile method for the modulation of 2-alkoxy side chain of 3-formylchromone enamines has been exploited for the synthesis of a series of 2-alkoxy-3-(sulfonylarylaminomethylene)-chroman-4-ones. This modulation was achieved by simply changing the alcoholic reaction media from methanol to ethanol, iso-propanol and n-butanol while reacting various 3-formylchromones with aminobenzenesulfonamides. Alcohols are sufficiently nucleophilic and add into the C2–C3 olefinic bond of 3-formylchromones without causing any ring cleavage. The resulting 2-alkoxy-3-(sulfonylarylaminomethylene)-chroman-4-ones were found to be potent and selective inhibitors of ecto-5′-nucleotidase and alkaline phosphatases (TNAP and IAP). Detailed enzyme kinetics studies revealed competitive inhibition against alkaline phosphatases and un-competitive inhibition against rat and human ecto-5′-nucleotidase. The most active TNAP inhibitor 23 ( K i = 0.078 ± 0.001 μM), exhibited 28 times more selectivity for TNAP over IAP ( K i = 2.18 ± 0.12 μM). Compound 9 was most active IAP inhibitor ( K i = 0.24 ± 0.01 μM), and was 300 times more selective towards IAP than TNAP ( K i = 72.9 ± 1.68 μM). Compound 40 was most active human ecto-5′-nucleotidase inhibitor exhibiting inhibition in low nanomolar range ( K i = 14 nM). [ABSTRACT FROM AUTHOR]

The steady-state kinetics of hydrolysis of four purine ribonucleotides: 3′-AMP, 5′-AMP, 5′-GMP and 5′-IMP catalysed by human prostatic acid phosphatase (PAP; EC 3.1.3.2) in vitro was examined in this study. It has been shown for the first time that nucleotidase activity of PAP exhibits positive cooperativity, or homotropic allostery, in binding the purine ribonucleotides. Therefore, these substrates are homotropic positive effectors, or homotropic allosteric activators, of PAP-catalysed reaction. Enzyme-substrate saturation curves described by Hill equation are sigmoidal and the values of Hill cooperativity coefficient h are higher than 1. The affinity of PAP to substrates, the degree of cooperativity and the efficiency all depend on the chemical nature of the ribonucleotide and they increase in the following order: 5′-AMP < 5′-IMP < 5′-GMP < 3′-AMP, but the enzyme reactivity remains almost equal. Therefore, 3′-AMP is the most efficient PAP substrate while 5′-AMP is the least efficient one of the four ribonucleotides studied. The noncovalent, homoallosteric regulation of the nucleotidase activity of PAP in vitro discovered in this study may be physiologically important in vivo . [ABSTRACT FROM AUTHOR]

Migration and positioning of immune cells is fundamental for their differentiation and recruitment at sites of infection. Besides the fundamental role played by chemokines and their receptors, recent studies demonstrate that a complex network of purinergic signaling events plays a key role in these trafficking events. This process includes the release of nucleotides (such as ATP and ADP) and subsequent autocrine and paracrine signaling events through nucleotide receptors. At the same time, surface-expressed ectoapyrases and nucleotidases convert extracellular nucleotides to adenosine, and adenosine signaling events play additional functional roles in leucocyte trafficking. In this review we revisit classical paradigms of inflammatory cell trafficking in the context of recent studies implicating purinergic signaling events in this process. [ABSTRACT FROM AUTHOR]

Trichomonas vaginalis is the aethiologic agent of trichomoniasis, the most common non-viral sexually transmitted disease in the world. The purinergic signaling pathway is mediated by extracellular nucleotides and nucleosides that are involved in many biological effects as neurotransmission, immunomodulation and inflammation. Extracellular nucleotides can be hydrolyzed by a family of enzymes known as ectonucleotidases including the ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) family which hydrolyses nucleosides triphosphate and diphosphate as preferential substrates and ecto-5′-nucleotidase which catalyzes the conversion of monophosphates into nucleosides. In T. vaginalis the E- NTPDase and ecto-5′-nucleotidase activities upon adenine nucleotides have already been characterized in intact trophozoites but little is known concerning guanine nucleotides and nucleoside. These enzymes may exert a crucial role on nucleoside generation, providing the purine sources for the synthesis de novo of these essential nutrients, sustaining parasite growth and survival. In this study, we investigated the hydrolysis profile of guanine-related nucleotides and nucleoside in intact trophozoites from long-term-grown and fresh clinical isolates of T. vaginalis. Knowing that guanine nucleotides are also substrates for T. vaginalis ectoenzymes, we evaluated the profile of nucleotides consumption and guanosine uptake in trophozoites submitted to a serum limitation condition. Results show that guanine nucleotides (GTP, GDP, GMP) were substrates for T. vaginalis ectonucleotidases, with expected kinetic parameters for this enzyme family. Different T. vaginalis isolates (two from the ATCC and nine fresh clinical isolates) presented a heterogeneous hydrolysis profile. The serum culture condition increased E-NTPDase and ecto-5′-nucleotidase activities with high consumption of extracellular GTP generating enhanced GDP, GMP and guanosine levels as demonstrated by HPLC, with final accumulation of the nucleoside. The transcript levels of the five TvNTPDases gene sequences were analyzed by qRT-PCR and the highest gene expressions were found for TvNTPDase 2 and 4 . The extracellular guanosine uptake was observed as 13C GTP nucleotide into parasite DNA and it was lower than that observed for adenosine, labeled as 13C ATP. These findings indicate the T. vaginalis preference for adenosine uptake and the accumulation of guanosine in the extracellular milieu, corroborating with HPLC data. Our data demonstrate, for the first time, the cascade of guanine nucleotides in T. vaginalis and open possibilities on the study of guanine-related purines other than the classical intracellular activity of G proteins for signal transduction. [ABSTRACT FROM AUTHOR]

Hyperbaric oxygen (HBO) is widely used in military operations, especially underwater missions. However, prolonged and continuous inhalation of HBO can cause central nervous system oxygen toxicity (CNS-OT), which greatly limits HBO׳s application. The regulation of astrocytes to the metabolism of adenosine is involved in epilepsy. In our study, we aimed to observe the effects of HBO exposure on the metabolism of adenosine in the brain. Furthermore, we aimed to confirm the possible mechanism underlying adenosine׳s mediation of the CNS-OT. Firstly, anesthetized rats exposed to 5 atm absolute HBO for 80 min. The concentrations of extracellular adenosine, ATP, ADP, and AMP were detected. Secondly, free-moving rats were exposed to HBO at the same pressure for 20 min, and the activities of 5’-nucleotidase and ADK in brain tissues were measured. For the mechanism studies, we observed the effects of a series of different doses of drugs related to adenosine metabolism on the latency of CNS-OT. Results showed HBO exposure could increase adenosine content by inhibiting ADK activity and improving 5′-nucleotidase activity. And adenosine metabolism during HBO exposure may be a protective response against HBO-induced CNS-OT. Moreover, the improvement of adenosine concentration, activation of adenosine A 1 R, or suppression of ADK and adenosine A 2A R, which are involved in the prevention of HBO-induced CNS-OT. This is the first study to demonstrate HBO exposure regulated adenosine metabolism in the brain. Adenosine metabolism and adenosine receptors are related to HBO-induced CNS-OT development. These results will provide new potential targets for the termination or the attenuation of CNS-OT. [ABSTRACT FROM AUTHOR]

Sporadic inclusion body myositis is the most frequent acquired myopathy of middle and later life and is distinguished from other inflammatory myopathies by its selective pattern of muscle involvement and slowly progressive course, and by the combination of inflammatory and degenerative muscle pathology and multi-protein deposits in muscle tissue. This review summarises the findings of recent studies that provide a more complete picture of the clinical phenotype and natural history of the disease and its global prevalence and genetic predisposition. Current diagnostic criteria, including the role of electrophysiological and muscle imaging studies and the recently identified anti-5′-nucleotidase (anti-cN1A) antibody in diagnosis are also discussed as well as current trends in the treatment of the disease. [ABSTRACT FROM AUTHOR]

Background Alterations in the activity of ectonucleotidase enzymes have been implicated in cardiovascular diseases, whereas regular exercise training has been shown to prevent these alterations. However, nothing is known about it relating to metabolic syndrome (MetS). We investigated the effect of exercise training on platelet ectonucleotidase enzymes and on the aggregation profile of MetS patients. Methods We studied 38 MetS patients who performed regular concurrent exercise training for 30 weeks. Anthropometric measurements, biochemical profiles, hydrolysis of adenine nucleotides in platelets and platelet aggregation were collected from patients before and after the exercise intervention as well as from individuals of the control group. Results An increase in the hydrolysis of adenine nucleotides (ATP, ADP and AMP) and a decrease in adenosine deamination in the platelets of MetS patients before the exercise intervention were observed ( P < 0.001). However, these alterations were reversed by exercise training ( P < 0.001). Additionally, an increase in platelet aggregation was observed in the MetS patients ( P < 0.001) and the exercise training prevented platelet hyperaggregation in addition to decrease the classic cardiovascular risks. Conclusions An alteration of ectonucleotidase enzymes occurs during MetS, whereas regular exercise training had a protective effect on these enzymes and on platelet aggregation. [ABSTRACT FROM AUTHOR]

Summary Escherichia coli 5′-nucleotidase is a two-domain enzyme exhibiting a unique 96° domain motion that is required for catalysis. Here we present an integrated structural biology study that combines DEER distance distributions with structural information from X-ray crystallography and computational biology to describe the population of presumably almost isoenergetic open and closed states in solution. Ensembles of models that best represent the experimental distance distributions are determined by a Monte Carlo search algorithm. As a result, predominantly open conformations are observed in the unliganded state indicating that the majority of enzyme molecules await substrate binding for the catalytic cycle. The addition of a substrate analog yields ensembles with an almost equal mixture of open and closed states. Thus, in the presence of substrate, efficient catalysis is provided by the simultaneous appearance of open conformers (binding substrate or releasing product) and closed conformers (enabling the turnover of the substrate). [ABSTRACT FROM AUTHOR]

Streptococcus pyogenes is an important human pathogen that causes a wide range of diseases. Using bioinformatics analysis of the complete S. pyogenes strain SF370 genome, we have identified a novel S. pyogenes virulence factor, which we termed streptococcal 5-nucleotidaseA(S5nA).Arecombinant form of S5nA hydrolyzed AMP and ADP, but not ATP, to generate the immunomodulatory molecule adenosine. Michaelis-Menten kinetics revealed a Km of 169μMand a Vmax of 7550 nmol/mg/min for the substrate AMP. Furthermore, recombinant S5nA acted synergistically with S. pyogenes nuclease A to generate macrophagetoxic deoxyadenosine from DNA. The enzyme showed optimal activity betweenpH5 andpH6.5 and between 37 and 47 °C. Like other 5'-nucleotidases, S5nA requires divalent cations and was active in the presence of Mg2+, Ca2+, or Mn2+. However, Zn2+ inhibited the enzymatic activity. Structural modeling combined with mutational analysis revealed a highly conserved catalytic dyad as well as conserved substrate and cation-binding sites. Recombinant S5nA significantly increased the survival of the non-pathogenic bacterium Lactococcus lactis during a human whole blood killing assay in a dose-dependent manner, suggesting a role as an S. pyogenes virulence factor. In conclusion, we have identified a novel S. pyogenes enzyme with 5-nucleotidase activity and immune evasion properties. [ABSTRACT FROM AUTHOR]

Adenine and uracil nucleotides play key functions in the autonomic nervous system (ANS). For instance, ATP acts as a neurotransmitter, co-transmitter and neuromodulator in the ANS. The purinergic system encompasses (1) receptors that respond to extracellular purines, which are designated as P1 and P2 purinoceptors, (2) purine release and uptake, and (3) a cascade of enzymes that regulate the concentration of purines near the cell surface. Ectonucleotidases and adenosine deaminase (ADA) are enzymes responsible for the hydrolysis of ATP (and other nucleotides such as ADP, UTP, UDP, AMP) and adenosine, respectively. Accordingly, these enzymes are expected to play an important role in the control of neuro-effector transmission in tissues innervated by both the sympathetic and parasympathetic divisions of the ANS. Indeed, ectonucleotidases have the ability to either terminate P2 receptor responses initiated by nucleoside triphosphates (ATP and UTP), and/or to favor the activation of ADP (e.g. P2Y 1,12,13 ) and UDP (e.g. P2Y 6 ) and/or adenosine (P1) specific receptors. In addition, ectonucleotidases can also importantly protect some P2 receptors from desensitization (e.g. P2X1, P2Y 1 ). In this review, we present the (putative) roles of ectonucleotidases and ADA in the ANS with a focus on their regulatory activity at neuro-effector junctions in the following tissues: heart, vas deferens, urinary bladder, salivary glands, blood vessels and the intestine. We also present their implication in nociceptive transmission. [ABSTRACT FROM AUTHOR]

Nucleotidases are phosphatases that catalyze the removal of phosphate from nucleotides, compounds with an important role in plant metabolism. A phosphatase enzyme, with high affinity for nucleotides monophosphate previously identified and purified in embryonic axes from French bean, has been analyzed by MALDI TOF/TOF and two internal peptides have been obtained. The information of these peptide sequences has been used to search in the genome database and only a candidate gene that encodes for the phosphatase was identified ( PvNTD1 ). The putative protein contains the conserved domains (motif I–IV) for haloacid dehalogenase-like hydrolases superfamily. The residues involved in the catalytic activity are also conserved. A recombinant protein overexpressed in Escherichia coli has shown molybdate resistant phosphatase activity with nucleosides monophosphate as substrate, confirming that the identified gene encodes for the phosphatase with high affinity for nucleotides purified in French bean embryonic axes. The activity of the purified protein was inhibited by adenosine. The expression of PvNTD1 gene was induced at the specific moment of radicle protrusion in embryonic axes. The gene was also highly expressed in young leaves whereas the level of expression in mature tissues was minimal. [ABSTRACT FROM AUTHOR]

Cytosolic 5′-nucleotidase II (cN-II) has been reported to be involved in cell survival, nucleotide metabolism and in the cellular response to anticancer drugs. With the aim to further evaluate the role of this enzyme in cell biology, we stably modulated its expression the human glioblastoma cell ADF in which the transient inhibition of cN-II has been shown to induce cell death. Stable cell lines were obtained both with inhibition, obtained with plasmids coding cN-II-targeting short hairpin RNA, and stimulation, obtained with plasmids coding Green Fluorescence Protein (GFP)-fused wild type cN-II or a GFP-fused hyperactive mutant (GFP-cN-II-R367Q), of cN-II expression. Silenced cells displayed a decreased proliferation rate while the over expressing cell lines displayed an increased proliferation rate as evidenced by impedance measurement using the xCELLigence device. The expression of nucleotide metabolism relevant genes was only slightly different between cell lines, suggesting a compensatory mechanism in transfected cells. Cells with decreased cN-II expression were resistant to the nucleoside analog fludarabine confirming the involvement of cN-II in the metabolism of this drug. Finally, we observed sensitivity to cisplatin in cN-II silenced cells and resistance to this same drug in cN-II over-expressing cells indicating an involvement of cN-II in the mechanism of action of platinum derivatives, and most probably in DNA repair. In summary, our findings confirm some previous data on the role of cN-II in the sensitivity of cancer cells to cancer drugs, and suggest its involvement in other cellular phenomenon such as cell proliferation. [ABSTRACT FROM AUTHOR]

Background Type II cytosolic 5′-nucleotidase (cN-II) catalyzes the hydrolysis of purine and, to some extent, of pyrimidine monophosphates. Recently, a number of papers demonstrated the involvement of cN-II in the mechanisms of resistance to antitumor drugs such as cytarabine, gemcitabine and fludarabine. Furthermore, cN-II is involved in drug resistance in patients affected by hematological malignancies influencing the clinical outcome. Although the implication of cN-II expression and/or activity appears to be correlated with drug resistance and poor prognosis, the molecular mechanism by which cN-II mediates drug resistance is still unknown. Methods HEK 293 cells carrying an expression vector coding for cN-II linked to green fluorescent protein (GFP) and a control vector without cN-II were utilized. A highly sensitive capillary electrophoresis method was applied for nucleotide pool determination and cytotoxicity exerted by drugs was determined with 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Results Over-expression of cN-II causes a drop of nucleoside triphosphate concentration and a general disturbance of nucleotide pool. Over-expressing cells were resistant to fludarabine, gemcitabine and cytarabine independently of cN-II ability to hydrolyze their monophosphates. Conclusions An increase of cN-II expression is sufficient to cause both a general disturbance of nucleotide pool and an increase of half maximal inhibitory concentration (IC 50 ) of the drugs. Since the monophosphates of cytarabine and gemcitabine are not substrates of cN-II, the protection observed cannot be directly ascribed to drug inactivation. General significance Our results indicate that cN-II exerts a relevant role in nucleotide and drug metabolism through not only enzyme activity but also a mechanism involving a protein–protein interaction, thus playing a general regulatory role in cell survival. Sentence Resistance to fludarabine, gemcitabine and cytarabine can be determined by an increase of cN-II both through dephosphorylation of active drugs and perturbation of nucleotide pool. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that inflammatory and immune mechanisms play important roles in the progression of chronic cerebral hypoperfusion (CCH)-induced white matter lesions (WMLs). As an endogenous neuromodulator in the brain, the extracellular levels of adenosine represent a critical endogenous mechanism for the regulation of immune and inflammatory responses. Ecto-5′-nucleotidase (CD73), which dephosphorylates AMP to adenosine, is considered to catalyze the rate-limiting step in the generation of extracellular adenosine. However, the role of CD73 in the development of CCH-induced WMLs remains unclear. In the present study, we investigated the expression and activity of CD73 using immunohistochemistry, Western blot analysis and measurements of the rate of AMP hydrolysis in a mouse model of CCH via bilateral common carotid artery stenosis (BCAS) surgery. Moreover, C57BL/6-CD73 knockout (KO) and their wild-type littermates were subjected to BCAS surgery to further investigate the functional roles of CD73 in the WMLs. White matter (WM) changes, astrocyte and microglia proliferation, proinflammatory cytokine levels in the corpus callosum and cognitive function were assessed on the 30th day after BCAS. The results indicated that CD73 expression and activities significantly increased in the corpus callosum on the 30th day after BCAS. Moreover, CD73 deficiency exacerbated CCH-induced WMLs and cognitive impairment. More reactive astrocytes and microglia were observed in the corpus callosum in CD73-KO mice. CD73 deficiency significantly increased the levels of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) in the BCAS model of CCH. These findings suggest that CD73 plays a protective role in the development of CCH-induced WMLs and cognitive impairment via the regulation of glial cell activation and proinflammatory cytokine expression. [ABSTRACT FROM AUTHOR]

Cell surface expression of specific receptors and ecto-nucleotidases makes extracellular nucleotides such as ATP, ADP, UTP, and adenosine suitable as signaling molecules for physiological and pathological events, including tissue stress and damage. Recent data have revealed the participation of purinergic signaling in atherosclerosis, depicting a scenario in which, in addition to some exceptions reflecting dual effects of individual receptor subtypes, adenosine and most P1 receptors, as well as ecto-nucleotidases, show a protective, anti-atherosclerotic function. By contrast, P2 receptors promote atherosclerosis. In consideration of these findings, modulation of purinergic signaling would represent an innovative and valuable tool to counteract atherosclerosis. We summarize recent developments on the participation of the purinergic network in atheroma formation and evolution. [ABSTRACT FROM AUTHOR]

Polyoxometalates (POMs) are inorganic cluster metal complexes that possess versatile biological activities, including antibacterial, anticancer, antidiabetic, and antiviral effects. Their mechanisms of action at the molecular level are largely unknown. However, it has been suggested that the inhibition of several enzyme families (e.g., phosphatases, protein kinases or ecto-nucleotidases) by POMs may contribute to their pharmacological properties. Ecto-nucleotidases are cell membrane-bound or secreted glycoproteins involved in the hydrolysis of extracellular nucleotides thereby regulating purinergic (and pyrimidinergic) signaling. They comprise four distinct families: ecto-nucleoside triphosphate diphosphohydrolases (NTPDases), ecto-nucleotide pyrophosphatases/phosphodiesterases (NPPs), alkaline phosphatases (APs) and ecto-5'-nucleotidase (eN). In the present study, we evaluated the inhibitory potency of a series of polyoxometalates as well as chalcogenide hexarhenium cluster complexes at a broad range of ecto-nucleotidases. [Co4(H2O)2(PW9O34)2]10- (5, PSB-POM142) was discovered to be the most potent inhibitor of human NTPDase1 described so far (Ki: 3.88 nM). Other investigated POMs selectively inhibited human NPP1, [TiW11CoO40]8- (4, PSB-POM141, Ki: 1.46 nM) and [NaSb9W21O86]18- (6, PSB-POM143, Ki: 4.98 nM) representing the most potent and selective human NPP1 inhibitors described to date. [NaP5W30O110]14- (8, PSB-POM144) strongly inhibited NTPDase1-3 and NPP1 and may therefore be used as a pan-inhibitor to block ATP hydrolysis. The polyoxoanionic compounds displayed a non-competitive mechanism of inhibition of NPPs and eN, but appeared to be competitive inhibitors of TNAP. Future in vivo studies with selected inhibitors identified in the current study are warranted. [ABSTRACT FROM AUTHOR]

5′-Nucleotidase (5′-NT) is widely represented in animal tissues (CD73) as well as in almost all snake venoms. In the present study, a 5′-NT isoform has been isolated from Vipera lebetina venom. The homodimeric isoform consists of monomers with molecular masses of 60 kDa. The enzyme is thermolabile and has pH optimum at 7.5. The 5′-NT activity is inhibited by metal ions Fe 3+ , Cu 2+ and Zn 2+ , enhanced by Mn 2+ while Mg 2+ and Ca 2+ have no remarkable effect. In addition to 120-kDa protein there are higher molecular forms of 5′-NT present in the V. lebetina venom. The cloning and sequencing of the 5′-NT coding cDNA resulted in 5′-truncated construct. MALDI-TOF and Orbitrap mass-spectrometry of the tryptic peptides confirmed the translated N-terminally truncated protein sequence concordance to the 5′-NT isolated from the venom. The isolated protein strongly inhibited ADP- or collagen-induced platelet aggregation. [ABSTRACT FROM AUTHOR]

Gemcitabine is the first-line treatment for pancreatic adenocarcinoma, but is increasingly used to treat breast, bladder, and non-small cell lung cancers. Despite such broad use, intrinsic and acquired chemoresistance is common. In general, the underlying mechanisms of chemoresistance are poorly understood. Here, current knowledge of gemcitabine metabolism, mechanisms of action, sensitivity and chemoresistance reported over the past two decades are reviewed; and we also offer new perspectives to improve gemcitabine efficacy with particular reference to the treatment of pancreatic cancer. [ABSTRACT FROM AUTHOR]

Abstract: Background: Subjects with Down syndrome (DS) have an increased susceptibility to infections and autoimmune disorders. ATP, adenosine, and acetylcholine contribute to the immune response regulation, and NTPDase, adenosine deaminase (ADA) and acetylcholinesterase (AChE) are important enzymes in the control of the extracellular levels of these molecules. We evaluated the activities of these enzymes and the cytokine levels in samples of DS individuals. Methods: The population consisted of 23 subjects with DS and 23 healthy subjects. Twelve milliliters of blood was obtained from each subject and used for lymphocyte and serum preparation. Lymphocytes were separated on Ficoll density gradients. After isolation, NTPDase and AChE activities were determined. Results: The NTPDase activity using ADP as substrate was increased in lymphocytes of DS patients compared to control (P <0.05); however, no alterations were observed in the ATP hydrolysis. An increase was observed in the AChE activity in lymphocytes and in ADA activity in serum of DS patients when compared to healthy subjects (P <0.05). In DS subjects, an increase in the levels of IL-1β, IL-6, TNF-α and IFN-γ and a decrease in the IL-10 levels were also observed (P <0.05). Conclusions: Alterations in the NTPDase, ADA and AChE activities as well changes in the cytokine levels may contribute to immunological alterations observed in DS. [Copyright &y& Elsevier]

Highlights: [•] UshA harbors major NAD degradation activity. [•] UshA acts as NAD pyrophosphatase and 5′-nucleotidase. [•] Deletion of the ushA gene improves NAD stability and promotes cell growth. [Copyright &y& Elsevier]

Abstract: The cytosolic 5′-nucleotidase II (cN-II) has been proposed as an attractive molecular target for the development of novel drugs circumventing resistance to cytotoxic nucleoside analogues currently used for treating leukemia and other malignant hemopathies. In the present work, synthesis of β-hydroxyphosphonate nucleoside analogues incorporating modifications either on the sugar residue or the nucleobase, and their in vitro evaluation towards the purified enzyme were carried out in order to determine their potency towards the inhibition of cN-II. In addition to the biochemical investigations, molecular modeling studies revealed important structural features for binding affinities towards the target enzyme. [Copyright &y& Elsevier]

Ecto-5′-nucleotidase (CD73) is well known for its implication in cancer. Inhibition of ecto-5′-nucleotidases is thought to provide an attractive approach to cancer therapy. This study identifies sulfonic acid compounds as efficient inhibitors of ecto-5′-nucleotidases. The compounds were tested against recombinant human and rat ecto-5′-nucleotidases. The most potent new sulfonic acid inhibitor 6-amino-4-hydroxynaphthalene-2-sulfonic acid (1) of ecto-5′-nucleotidase had an IC50 of 1.32 ± 0.09 μM for the human and 10.4 ± 3.3 μM for the rat enzyme. Generally, all compounds were more active against the human enzyme. Plausible binding mode models were developed for this new class of inhibitors. Furthermore, several sulfonic acid inhibitors were efficient cytotoxic agents when tested on H157 cancer cell lines. Hence, new ecto-5′-nucleotidases inhibitors displayed significant potential for further development as compounds for anti-cancer therapy. [ABSTRACT FROM AUTHOR]

Abstract: Extracellular adenosine triphosphate (ATP) is sequentially dephosphorylated by two ectoenzymes: CD39/nucleotidase triphosphate dephosphorylase (ENTPD) and CD73/5′-ectonucleotidase (5′-NT). Adenosine, its notable metabolite, may elicit potent anti-inflammatory responses. We examined whether the CD39-adenosinergic axis may exist in gingival fibroblasts and have an effect on the expression of matrix metalloproteinase (MMP)-1, the excess production of which leads to pathological matrix degradation. We showed that transcripts of CD39, CD73, and adenosine receptors A1, A2a, and A2b, but not A3, were expressed by human gingival fibroblasts by RT-PCR. We also identified the expression of CD39 in fibroblastic cells in rat gingiva by immunohistochemistry. ATP inhibited the expression of MMP-1 triggered by interleukin-1 at gene and protein levels. However, ATP-γS, a stable ATP analog, did not. The ATP-mediated MMP-1 inhibition was restored in the presence of POM-1, a specific ENTPD inhibitor, suggesting that CD39/ENTPD was involved in the MMP-1 inhibition. ATP metabolites including adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), and adenosine inhibited MMP-1 expression, but ADP-βS, a stable ADP, did not, suggesting that adenosine converted from ATP by the action of CD39/ENTPD and CD73/5′-NT may contribute to MMP-1 inhibition. Adenosine-mediated MMP-1 inhibition was restored in the presence of H89, a protein kinase A (PKA) inhibitor. Conversely, forskolin, an enhancer of intracellular cAMP, mimicked the effect of adenosine, suggesting that the cAMP/PKA signaling pathway is involved in adenosine-mediated MMP-1 inhibition. The present findings suggest the existence of an endogenous anti-tissue destructive mechanism in gingival tissue via the CD39-adenosinergic axis. [Copyright &y& Elsevier]

Abstract: The enzyme ecto-5′-nucleotidase (e5NT, CD73), a metallophosphoesterase, is a critical component of adenosine metabolism and signaling and implicated in different disease states. Therefore, attempts have been made to discover inhibitors of e5NT. For example, a virtual screening study using a molecular model of the enzyme has led to the identification of a new series of sulfonamide-containing e5NT inhibitors. The recent availability of several X-ray structures of human e5NT in complex with inhibitors has made it possible to re-evaluate this model building and virtual screening effort. We have assessed the quality of the model in detail and analyzed the question why it was possible to identify a new series of inhibitors on the basis of model-based docking calculations. The model utilized for virtual screening was found to be topologically correct and approach experimental accuracy in the active site region. Two key features within the active site were identified as major determinants for the successfully identification of inhibitors. Taken together, the results rationalize the computer-aided discovery of sulfonamide inhibitors of e5NT and provide further support for the use of carefully built protein models for virtual screening. [Copyright &y& Elsevier]