Recombinant expression of ecto-nucleotide pyrophosphatase/phosphodiesterase 4 (NPP4) and development of a luminescence-based assay to identify inhibitors

Heparins are potent inhibitors of ectonucleotide pyrophosphatase/phospho-diesterase-1 (NPP1) - a promising target for the immunotherapy of cancer

Introduction

Heparins, naturally occurring glycosaminoglycans, are widely used for thrombosis prevention. Upon application as anticoagulants in cancer patients, heparins were found to possess additional antitumor activities. Ectonucleotidases have recently been proposed as novel targets for cancer immunotherapy.

Methods and results

In the present study, we discovered that heparin and its derivatives act as potent, selective, allosteric inhibitors of the poorly investigated ectonucleotidase NPP1 (nucleotide pyrophosphatase/phosphodiesterase-1, CD203a). Structure-activity relationships indicated that NPP1 inhibition could be separated from the compounds' antithrombotic effect. Moreover, unfractionated heparin (UFH) and different low molecular weight heparins (LMWHs) inhibited extracellular adenosine production by the NPP1-expressing glioma cell line U87 at therapeutically relevant concentrations. As a consequence, heparins inhibited the ability of U87 cell supernatants to induce CD4+ T cell differentiation into immunosuppressive Treg cells.

Discussion

NPP1 inhibition likely contributes to the anti-cancer effects of heparins, and their specific optimization may lead to improved therapeutics for the immunotherapy of cancer.

Effects of physical exercise on the functionality of human nucleotidases: A systematic review

Nucleotidases contribute to the regulation of inflammation, coagulation, and cardiovascular activity. Exercise promotes biological adaptations, but its effects on nucleotidase activities and expression are unclear. The objective of this study was to review systematically the effects of exercise on nucleotidase functionality in healthy and unhealthy subjects. The MEDLINE, EMBASE, Cochrane Library, and Web of Science databases were searched to identify, randomized clinical trials, non-randomized clinical trials, uncontrolled clinical trials, quasi-experimental, pre-, and post-interventional studies that evaluated the effects of exercise on nucleotidases in humans, and was not limited by language and date. Two independent reviewers performed the study selection, data extraction, and assessment of risk of bias. Of the 203 articles identified, 12 were included in this review. Eight studies reported that acute exercise, in healthy and unhealthy subjects, elevated the activities or expression of nucleotidases. Four studies evaluated the effects of chronic training on nucleotidase activities in the platelets and lymphocytes of patients with metabolic syndrome, chronic kidney disease, and hypertension and found a decrease in nucleotidase activities in these conditions. Acute and chronic exercise was able to modify the blood plasma and serum levels of nucleotides and nucleosides. Our results suggest that short- and long-term exercise modulate nucleotidase functionality. As such, purinergic signaling may represent a novel molecular adaptation in inflammatory, thrombotic, and vascular responses to exercise.

Protein kinase inhibitor ceritinib blocks ectonucleotidase CD39 - a promising target for cancer immunotherapy

Background

An important mechanism, by which cancer cells achieve immune escape, is the release of extracellular adenosine into their microenvironment. Adenosine activates adenosine A_2A and A_2B receptors on immune cells constituting one of the strongest immunosuppressive mediators. In addition, extracellular adenosine promotes angiogenesis, tumor cell proliferation, and metastasis. Cancer cells upregulate ectonucleotidases, most importantly CD39 and CD73, which catalyze the hydrolysis of extracellular ATP to AMP (CD39) and further to adenosine (CD73). Inhibition of CD39 is thus expected to be an effective strategy for the (immuno)therapy of cancer. However, suitable small molecule inhibitors for CD39 are not available. Our aim was to identify drug-like CD39 inhibitors and evaluate them in vitro.

Methods

We pursued a repurposing approach by screening a self-compiled collection of approved, mostly ATP-competitive protein kinase inhibitors, on human CD39. The best hit compound was further characterized and evaluated in various orthogonal assays and enzyme preparations, and on human immune and cancer cells.

Results

The tyrosine kinase inhibitor ceritinib, a potent anticancer drug used for the treatment of anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer, was found to strongly inhibit CD39 showing selectivity versus other ectonucleotidases. The drug displays a non-competitive, allosteric mechanism of CD39 inhibition exhibiting potency in the low micromolar range, which is independent of substrate (ATP) concentration. We could show that ceritinib inhibits ATP dephosphorylation in peripheral blood mononuclear cells in a dose-dependent manner, resulting in a significant increase in ATP concentrations and preventing adenosine formation from ATP. Importantly, ceritinib (1–10 µM) substantially inhibited ATP hydrolysis in triple negative breast cancer and melanoma cells with high native expression of CD39.

Conclusions

CD39 inhibition might contribute to the effects of the powerful anticancer drug ceritinib. Ceritinib is a novel CD39 inhibitor with high metabolic stability and optimized physicochemical properties; according to our knowledge, it is the first brain-permeant CD39 inhibitor. Our discovery will provide the basis (i) to develop more potent and balanced dual CD39/ALK inhibitors, and (ii) to optimize the ceritinib scaffold towards interaction with CD39 to obtain potent and selective drug-like CD39 inhibitors for future in vivo studies.

Beyond Triphosphates: Reagents and Methods for Chemical Oligophosphorylation

Oligophosphates play essential roles in biochemistry, and considerable research has been directed toward the synthesis of both naturally occurring oligophosphates and their synthetic analogues. Greater attention has been given to mono-, di-, and triphosphates, as these are present in higher concentrations biologically and easier to synthesize. However, extended oligophosphates have potent biochemical roles, ranging from blood coagulation to HIV drug resistance. Sporadic reports have slowly built a niche body of literature related to the synthesis and study of extended oligophosphates, but newfound interests and developments have the potential to rapidly expand this field. Here we report on current methods to synthesize oligophosphates longer than triphosphates and comment on the most important future directions for this area of research. The state of the art has provided fairly robust methods for synthesizing nucleoside 5'-tetra- and pentaphosphates as well as dinucleoside 5',5'-oligophosphates. Future research should endeavor to push such syntheses to longer oligophosphates while developing synthetic methodologies for rarer morphologies such as 3'-nucleoside oligophosphates, polyphosphates, and phosphonate/thiophosphate analogues of these species.

Nucleotide pyrophosphatase/phosphodiesterases (NPPs) including NPP1 and NPP2/ ATX as important drug targets: A patent review (2015-2020)

INTRODUCTION

Nucleoside triphosphate diphosphohydrolases (NTPDases), alkaline phosphatases (APs), and ecto-nucleotide pyrophosphatases/phosphodiesterases (NPPs) are nucleotidases found on the cell surface. It is a promising therapeutic target for a range of disorders, including fibrosis, tumour metastasis, pruritus, inflammation, multiple sclerosis, and autoimmune diseases. As a result, therapeutic intervention including selective inhibitors of NPPs is required.

AREA COVERED

Many chemical substances, including pyrazole, pyridine and bicyclic compounds have demonstrated promising inhibitory potential for ecto-nucleotide pyrophosphatase/phosphodiesterases. The chemistry and clinical applications of NPPs inhibitors patented between 2015 and 2020 are discussed in this review.

EXPERT OPINION

: In recent years, there has been a lot of effort put into finding effective and selective inhibitors of NPPs. Despite the fact that a variety of synthetic inhibitors have been created, only a few investigations on their in vivo activity have been published. In addition to IOA-289 which has passed Phase Ia clinical trials; potent ATX inhibitor compounds such as BLD-0409, IPF and BBT-877 have been placed in phase I clinical studies. Some of the most promising ATX inhibitors in recent years are closely related analogs of previously known inhibitors, such as PF-8380. Knowledge of the structure activity relationship of such promising inhibitors can potentially translate into the discovery of more potent and effective inhibitors of NPP with a variety of structural characteristics and favourable therapeutic activities.

2-Substituted thienotetrahydropyridine derivatives: Allosteric ectonucleotidase inhibitors

The antithrombotic prodrugs ticlopidine and clopidogrel are thienotetrahydro-pyridine derivatives that are metabolized in the liver to produce thiols that irreversibly block adenosine diphosphate (ADP)-activated P2Y₁₂ receptors on thrombocytes. In their native, nonmetabolized form, both drugs were reported to act as inhibitors of ectonucleoside triphosphate diphosphohydrolase-1 (NTPDase1, CD39). CD39 catalyzes the extracellular hydrolysis of nucleoside tri- and diphosphates, mainly adenosine 5'-triphosphate (ATP) and ADP, yielding adenosine monophosphate, which is further hydrolyzed by ecto-5'-nucleotidase (CD73) to produce adenosine. While ATP has proinflammatory effects, adenosine is a potent anti-inflammatory, immunosuppressive agent. Inhibitors of CD39 and CD73 have potential as novel checkpoint inhibitors for the immunotherapy of cancer and infection. In the present study, we investigated 2-substituted thienotetrahydropyridine derivatives, structurally related to ticlopidine, as CD39 inhibitors. Due to their substituent on the 2-position, they will not be metabolically transformed into reactive thiols and can, therefore, be expected to be devoid of P2Y₁₂ receptor-antagonistic activity in vivo. Several of the investigated 2-substituted thienotetrahydropyridine derivatives showed concentration-dependent inhibition of CD39. The most potent derivative, 32, showed similar CD39-inhibitory potency to ticlopidine, both acting as allosteric inhibitors. Compound 32 showed an improved selectivity profile: While ticlopidine blocked several NTPDase isoenzymes, 32 was characterized as a novel dual inhibitor of CD39 and CD73.

Discovery of potent nucleotide pyrophosphatase/phosphodiesterase3 (NPP3) inhibitors with ancillary carbonic anhydrase inhibition for cancer (immuno)therapy

Nucleotide pyrophosphatase/phosphodiesterase3 (NPP3) catalyzes the hydrolysis of extracellular nucleotides. It is expressed by immune cells and some carcinomas, e.g. of kidney and colon. Together with ecto-5'-nucleotidase (CD73), NPP3 produces immunosuppressive, cancer-promoting adenosine, and has therefore been proposed as a target for cancer therapy. Here we report on the discovery of 4-[(4-methylphthalazin-1-yl)amino]benzenesulfonamide (1) as an inhibitor of human NPP3 identified by compound library screening. Subsequent structure-activity relationship (SAR) studies led to the potent competitive NPP3 inhibitor 2-methyl-5-{4-[(4-sulfamoylphenyl)amino]phthalazin-1-yl}benzenesulfonamide (23, K i 53.7 nM versus the natural substrate ATP). Docking studies predicted its binding pose and interactions. While 23 displayed high selectivity versus other ecto-nucleotidases, it showed ancillary inhibition of two proposed anti-cancer targets, the carbonic anhydrases CA-II (Ki 74.7 nM) and CA-IX (Ki 20.3 nM). Thus, 23 may act as multi-target anti-cancer drug. SARs for NPP3 were steeper than for CAs leading to the identification of potent dual CA-II/CA-IX (e.g. 34) as well as selective CA-IX inhibitors (e.g. 31).

Acute moderate-intensity aerobic exercise promotes purinergic and inflammatory responses in sedentary, overweight and physically active subjects

NEW FINDING

What is the central question of this study? How does moderate-intensity aerobic exercise affect the behaviour of purinergic enzymes in sedentary, overweight and physically active subjects? What is the relationship between purinergic and inflammatory responses triggered by exercise? What is the main finding and its importance? Moderate-intensity aerobic exercise modifies the activity of purinergic enzymes and the levels of nucleotides and nucleosides. These results are similar in subjects with different biological characteristics. 5'-Nucleotidase activity and adenosine levels are associated with inflammatory responses. This study suggests that a purinergic pathway is related to the inflammatory responses triggered by exercise.

ABSTRACT

Purinergic signalling is a mechanism of extracellular communication that modulates events related to exercise, such as inflammation and coagulation. Herein, we evaluated the effects of acute moderate-intensity exercise on the activities of purinergic enzymes and plasma levels of adenine nucleotides in individuals with distinct metabolic characteristics. We analysed the relationship between purinergic parameters, inflammatory responses and cardiometabolic markers. Twenty-four healthy males were assigned to three groups: normal weight sedentary (n = 8), overweight sedentary (n = 8) and normal weight physically active (n = 8). The volunteers performed an acute session of moderate-intensity aerobic exercise on a treadmill at 70% of V ̇ O 2 peak ; blood samples were drawn at baseline, immediately post-exercise and at 1 h post-exercise. Immediately post-exercise, all subjects showed increases in ATP, ADP, AMP and p-nitrophenyl thymidine 5'-monophosphate hydrolysis, while AMP hydrolysis remained increased at 1 h after exercise. High-performance liquid chromatography analysis demonstrated lower levels of ATP and ADP at post- and 1 h post-exercise in all groups. Conversely, adenosine and inosine levels increased at post-exercise, but only adenosine remained augmented at 1 h after exercise in all groups. With regard to inflammatory responses, the exercise protocol increased tumour necrosis factor α (TNF-α) and interleukin 8 (IL-8) concentrations in all subjects, but only TNF-α remained elevated at 1 h after exercise. Significant correlations were found between the activity of 5'-nucleotidase, adenosine levels, V ̇ O 2 peak , triglyceride, TNF-α and IL-8 levels. Our findings suggest a purinergic signalling pathway that participates, at least partially, in the inflammatory responses triggered by acute moderate-intensity exercise. The response of soluble nucleotidases to acute moderate exercise appears to be similar between subjects of different biological profiles.

Sulfated Polysaccharides from Macroalgae Are Potent Dual Inhibitors of Human ATP-Hydrolyzing Ectonucleotidases NPP1 and CD39

Extracellular ATP mediates proinflammatory and antiproliferative effects via activation of P2 nucleotide receptors. In contrast, its metabolite, the nucleoside adenosine, is strongly immunosuppressive and enhances tumor proliferation and metastasis. The conversion of ATP to adenosine is catalyzed by ectonucleotidases, which are expressed on immune cells and typically upregulated on tumor cells. In the present study, we identified sulfopolysaccharides from brown and red sea algae to act as potent dual inhibitors of the main ATP-hydrolyzing ectoenzymes, ectonucleotide pyrophosphatase/phosphodiesterase-1 (NPP1) and ecto-nucleoside triphosphate diphosphohydrolase-1 (NTPDase1, CD39), showing nano- to picomolar potency and displaying a non-competitive mechanism of inhibition. We showed that one of the sulfopolysaccharides tested as a representative example reduced adenosine formation at the surface of the human glioblastoma cell line U87 in a concentration-dependent manner. These natural products represent the most potent inhibitors of extracellular ATP hydrolysis known to date and have potential as novel therapeutics for the immunotherapy of cancer.

Recent achievements of bioluminescence imaging based on firefly luciferin-luciferase system

Bioluminescence imaging (BLI) is a newly developed noninvasive visual approach which facilitates the understanding of a plethora of biological processes in vitro and in vivo due to the high sensitivity, resolution and selectivity, low background signal, and the lack of external light excitation. BLI based on firefly luciferin-luciferase system has been widely used for the activity evaluation of tumor-specific enzymes, for the detection of diseases-related bioactive small molecules and metal ions, and for the diagnosis and therapy of diseases including the studies of drug transport, the research of immune response, and the evaluation of drug potency and tissue distribution. In this review, we highlight the recent achievements in luciferin derivatives with red-shifted emission spectra, mutant luciferase-luciferin pairs, and the diagnostic and therapeutic application of BLI based on firefly luciferin-luciferase system. The development and application of BLI will expand our knowledge of the occurrence and development of diseases and shed light on the diagnosis and treatment of various diseases.

History of ectonucleotidases and their role in purinergic signaling

Ectonucleotidases are key for purinergic signaling. They control the duration of activity of purinergic receptor agonists. At the same time, they produce hydrolysis products as additional ligands of purinergic receptors. Due to the considerable diversity of enzymes, purinergic receptor ligands and purinergic receptors, deciphering the impact of extracellular purinergic receptor control has become a challenge. The first group of enzymes described were the alkaline phosphatases - at the time not as nucleotide-metabolizing but as nonspecific phosphatases. Enzymes now referred to as nucleoside triphosphate diphosphohydrolases and ecto-5'-nucleotidase were the first and only nucleotide-specific ectonucleotidases identified. And they were the first group of enzymes related to purinergic signaling. Additional research brought to light a surprising number of ectoenzymes with broad substrate specificity, which can also hydrolyze nucleotides. This short overview traces the development of the field and briefly highlights important results and benefits for therapies of human diseases achieved within nearly a century of investigations.

Nucleotide Analog ARL67156 as a Lead Structure for the Development of CD39 and Dual CD39/CD73 Ectonucleotidase Inhibitors

Nucleoside triphosphate diphosphohydrolase1 (NTPDase1, CD39) inhibitors have potential as novel drugs for the (immuno)therapy of cancer. They increase the extracellular concentration of immunostimulatory ATP and reduce the formation of AMP, which can be further hydrolyzed by ecto-5'-nucleotidase (CD73) to immunosuppressive, cancer-promoting adenosine. In the present study, we synthesized analogs and derivatives of the standard CD39 inhibitor ARL67156, a nucleotide analog which displays a competitive mechanism of inhibition. Structure-activity relationships were analyzed at the human enzyme with respect to substituents in the N ⁶- and C8-position of the adenine core, and modifications of the triphosph(on)ate chain. Capillary electrophoresis coupled to laser-induced fluorescence detection employing a fluorescent-labeled ATP derivative was employed to determine the compounds' potency. Selected inhibitors were additionally evaluated in an orthogonal, malachite green assay versus the natural substrate ATP. The most potent CD39 inhibitors of the present series were ARL67156 and its derivatives 31 and 33 with K_i values of around 1 µM. Selectivity studies showed that all three nucleotide analogs additionally blocked CD73 acting as dual-target inhibitors. Docking studies provided plausible binding modes to both targets. The present study provides a full characterization of the frequently applied CD39 inhibitor ARL67156, presents structure-activity relationships, and provides a basis for future optimization towards selective CD39 and dual CD39/CD73 inhibitors.