A selective high-affinity antagonist of the P2Y14 receptor inhibits UDP-glucose-stimulated chemotaxis of human neutrophils

Recent advances in the development of P2Y14R inhibitors: a patent and literature review (2018-present)

INTRODUCTION

The P2Y14 receptor (P2Y14R), a member of the G protein-coupled receptor family, is activated by extracellular nucleotides. Due to its involvement in inflammatory, immunological and other associated processes, P2Y14R has emerged as a promising therapeutic target. Despite lacking a determined three-dimensional crystal structure, the homology modeling technique based on closely related P2Y receptors' crystallography has been extensively utilized for developing active compounds targeting P2Y14R. Recent discoveries have unveiled numerous highly effective and subtype-specific P2Y14R inhibitors. This study presents an overview of the latest advancements in P2Y14R inhibitors.

AREAS COVERED

This review presents an overview of the advancements in P2Y14R inhibitor research over the past five years, encompassing new patents, journal articles, and highlighting the therapeutic prospects inherent in these compounds.

EXPERT OPINION

The recent revelation of the vast potential of P2Y14R inhibitors has led to the development of novel compounds that exhibit promising capabilities for the treatment of sterile inflammation of the kidney, potentially diabetes, and asthma. Despite being a relatively nascent class of compounds, certain members have already exhibited their capacity to surmount specific challenges posed by conventional P2Y14R inhibitors. Targeting P2Y14R through small molecules may present a promising therapeutic strategy for effectively managing diverse inflammatory diseases.

Pharmacological characterization of P2Y receptor subtypes - an update

P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular nucleotides. There are eight mammalian P2Y receptor subtypes (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13, and P2Y14). The widely expressed P2Y receptors play important roles in physiology and pathophysiology. This review summarizes the use of pharmacological tools to characterize the P2Y receptor subtypes involved in these responses. MRS2500 is a potent and selective antagonist acting at the P2Y1 receptor. AR-C118925 is useful for the selective antagonism of the P2Y2 receptor. PSB16133 blocks the P2Y4 receptor, MRS2578 is an antagonist at the P2Y6 receptor and NF157 as well as NF340 block the P2Y11 receptor. ADP-induced platelet aggregation is mediated by P2Y1 and P2Y12 receptors. A number of compounds or their active metabolites reduce ADP-induced platelet aggregation by blocking the P2Y12 receptor. These include the active metabolites of the thienopyridine compounds clopidogrel and prasugrel, the nucleoside analogue ticagrelor and the nucleotide analogue cangrelor. PSB0739 is also a potent antagonist at the P2Y12 receptor useful for both in vitro and in vivo studies. MRS2211 and MRS2603 inhibit P2Y13 mediated responses. PPTN is a very potent antagonist at the P2Y14 receptor.

Identification of a carbohydrate recognition motif of purinergic receptors

As a major class of biomolecules, carbohydrates play indispensable roles in various biological processes. However, it remains largely unknown how carbohydrates directly modulate important drug targets, such as G-protein coupled receptors (GPCRs). Here, we employed P2Y purinoceptor 14 (P2Y14), a drug target for inflammation and immune responses, to uncover the sugar nucleotide activation of GPCRs. Integrating molecular dynamics simulation with functional study, we identified the uridine diphosphate (UDP)-sugar-binding site on P2Y14, and revealed that a UDP-glucose might activate the receptor by bridging the transmembrane (TM) helices 2 and 7. Between TM2 and TM7 of P2Y14, a conserved salt bridging chain (K2.60-D2.64-K7.35-E7.36 [KDKE]) was identified to distinguish different UDP-sugars, including UDP-glucose, UDP-galactose, UDP-glucuronic acid, and UDP-N-acetylglucosamine. We identified the KDKE chain as a conserved functional motif of sugar binding for both P2Y14 and P2Y purinoceptor 12 (P2Y12), and then designed three sugar nucleotides as agonists of P2Y12. These results not only expand our understanding for activation of purinergic receptors but also provide insights for the carbohydrate drug development for GPCRs.

Uridine Diphosphate Glucose (UDP-G) Activates Oxidative Stress and Respiratory Burst in Isolated Neutrophils

The extracellular purinergic agonist uridine diphosphate glucose (UDP-G) activates chemotaxis of human neutrophils (PMN) and the recruitment of PMN at the lung level, via P2Y14 purinergic receptor signaling. This effect is similar to the activation of PMN with N-formyl-methionyl-leucyl-phenylalanine (fMLP), a mechanism that also triggers the production of superoxide anion and hydrogen peroxide via the NADPH oxidase system. However, the effects of UDP-G on this system have not been studied. Defects in the intracellular phagocyte respiratory burst (RB) cause recurrent infections, immunodeficiency, and chronic and severe diseases in affected patients, often with sepsis and hypoxia. The extracellular activation of PMN by UDP-G could affect the RB and oxidative stress (OS) in situations of inflammation, infection and/or sepsis. The association of PMNs activation by UDP-G with OS and RB was studied. OS was evaluated by measuring spontaneous chemiluminescence (CL) of PMNs with a scintillation photon counter, and RB by measuring oxygen consumption with an oxygen Clark electrode at 37 °C, in non-stimulated cells and after activation (15 min) with lipopolysaccharides (LPS, 2 µg/mL), phorbol myristate acetate (PMA, 20 ng/mL), or UDP-G (100 μM). The stimulation index (SI) was calculated in order to establish the activation effect of the three agonists. After stimulation with LPS or PMA, the activated PMNs (0.1 × 106 cells/mL) showed an increase in CL (35%, p < 0.05 and 56%, p < 0.01, SI of 1.56 and 2.20, respectively). Contrariwise, the stimulation with UDP-G led to a decreased CL in a dose-dependent manner (60%, 25 μM, p < 0.05; 90%, 50-150 μM, p < 0.001). Nonetheless, despite the lack of oxidative damage, UDP-G triggered RB (SI 1.8) in a dose-dependent manner (38-50%, 100-200 μM, p < 0.0001). UDP-G is able to trigger NADPH oxidase activation in PMNs. Therefore, the prevention of OS and oxidative damage observed upon PMN stimulation with UDP-G indicates an antioxidant property of this molecule which is likely due to the activation of antioxidant defenses. Altogether, LPS and UDP-G have a synergistic effect, suggesting a key role in infection and/or sepsis.

Pharmacological interaction and immune response of purinergic receptors in therapeutic modulation

Nucleosides and purine nucleotides serve as transmitter and modulator agents that extend their functions beyond the cell. In this context, purinergic signaling plays a crucial role in regulating energy homeostasis and modulating metabolic alterations in tumor cells. Therefore, it is essential to consider the pharmacological targeting of purinergic receptors (PUR), which encompass the expression and inhibition of P1 receptors (metabotropic adenosine receptors) as well as P2 receptors (extracellular ATP/ADP) comprising P2X and P2Y receptors. Thus, the pharmacological interaction between inhibitors (such as RNA, monoclonal antibodies, and small molecules) and PUR represents a key aspect in facilitating the development of therapeutic interventions. Moreover, this review explores recent advancements in pharmacological inhibitors and the regulation of innate and adaptive immunity of PUR, specifically in relation to immunological and inflammatory responses. These responses encompass the release of pro-inflammatory cytokines (PIC), the production of reactive oxygen and nitrogen species (ROS and RNS), the regulation of T cells, and the activation of inflammasomes in all human leukocytes.

Alicyclic Ring Size Variation of 4-Phenyl-2-naphthoic Acid Derivatives as P2Y14 Receptor Antagonists

P2Y14 receptor (P2Y14R) is activated by extracellular UDP-glucose, a damage-associated molecular pattern that promotes inflammation in the kidney, lung, fat tissue, and elsewhere. Thus, selective P2Y14R antagonists are potentially useful for inflammatory and metabolic diseases. The piperidine ring size of potent, competitive P2Y14R antagonist (4-phenyl-2-naphthoic acid derivative) PPTN 1 was varied from 4- to 8-membered rings, with bridging/functional substitution. Conformationally and sterically modified isosteres included N-containing spirocyclic (6-9), fused (11-13), and bridged (14, 15) or large (16-20) ring systems, either saturated or containing alkene or hydroxy/methoxy groups. The alicyclic amines displayed structural preference. An α-hydroxyl group increased the affinity of 4-(4-((1R,5S,6r)-6-hydroxy-3-azabicyclo[3.1.1]heptan-6-yl)phenyl)-7-(4-(trifluoromethyl)phenyl)-2-naphthoic acid 15 (MRS4833) compared to 14 by 89-fold. 15 but not its double prodrug 50 reduced airway eosinophilia in a protease-mediated asthma model, and orally administered 15 and prodrugs reversed chronic neuropathic pain (mouse CCI model). Thus, we identified novel drug leads having in vivo efficacy.

Reduced urine volume and changed renal sphingolipid metabolism in P2ry14-deficient mice

The UDP-glucose receptor P2RY14, a rhodopsin-like G protein-coupled receptor (GPCR), was previously described as receptor expressed in A-intercalated cells of the mouse kidney. Additionally, we found P2RY14 is abundantly expressed in mouse renal collecting duct principal cells of the papilla and epithelial cells lining the renal papilla. To better understand its physiological function in kidney, we took advantage of a P2ry14 reporter and gene-deficient (KO) mouse strain. Morphometric studies showed that the receptor function contributes to kidney morphology. KO mice had a broader cortex relative to the total kidney area than wild-type (WT) mice. In contrast, the area of the outer stripe of the outer medulla was larger in WT compared to KO mice. Transcriptome comparison of the papilla region of WT and KO mice revealed differences in the gene expression of extracellular matrix proteins (e.g., decorin, fibulin-1, fibulin-7) and proteins involved in sphingolipid metabolism (e.g., small subunit b of the serine palmitoyltransferase) and other related GPCRs (e.g., GPR171). Using mass spectrometry, changes in the sphingolipid composition (e.g., chain length) were detected in the renal papilla of KO mice. At the functional level, we found that KO mice had a reduced urine volume but an unchanged glomerular filtration rate under normal chow and salt diets. Our study revealed P2ry14 as a functionally important GPCR in collecting duct principal cells and cells lining the renal papilla and the possible involvement of P2ry14 in nephroprotection by regulation of decorin.

A host defense peptide mimetic, brilacidin, potentiates caspofungin antifungal activity against human pathogenic fungi

Fungal infections cause more than 1.5 million deaths a year. Due to emerging antifungal drug resistance, novel strategies are urgently needed to combat life-threatening fungal diseases. Here, we identify the host defense peptide mimetic, brilacidin (BRI) as a synergizer with caspofungin (CAS) against CAS-sensitive and CAS-resistant isolates of Aspergillus fumigatus, Candida albicans, C. auris, and CAS-intrinsically resistant Cryptococcus neoformans. BRI also potentiates azoles against A. fumigatus and several Mucorales fungi. BRI acts in A. fumigatus by affecting cell wall integrity pathway and cell membrane potential. BRI combined with CAS significantly clears A. fumigatus lung infection in an immunosuppressed murine model of invasive pulmonary aspergillosis. BRI alone also decreases A. fumigatus fungal burden and ablates disease development in a murine model of fungal keratitis. Our results indicate that combinations of BRI and antifungal drugs in clinical use are likely to improve the treatment outcome of aspergillosis and other fungal infections.

Effects of uridine and nucleotides on hemostasis parameters

Several purinergic receptors have been identified on platelets which are involved in hemostatic and thrombotic processes. The aim of the present study was to investigate the effects of uridine and its nucleotides on platelet aggregation and hemostasis in platelet-rich plasma (PRP) and whole blood. The effects of uridine, UMP, UDP, and UTP at different final concentrations (1 to 1000 µM) on platelet aggregation were studied using an aggregometer. In PRP samples, platelet aggregation was induced by ADP, collagen and epinephrine 3 min after addition of uridine, UMP, UDP, UTP and saline (as a control). All thromboelastogram experiments were performed at 1000 µM final concentrations of uridine and its nucleotides in whole blood. UDP and UTP were also tested in thromboelastogram with PRP. Our results showed that UDP, and especially UTP, inhibited ADP- and collagen-induced aggregation in a concentration-dependent manner. In whole blood thromboelastogram experiments, UDP stimulated clot formation while UTP suppressed clot formation. When thromboelastogram experiments were repeated with PRP, UTP's inhibitory effect on platelets was confirmed, while UDP's stimulated clot forming effect disappeared. Collectively, our data showed that UTP inhibited platelet aggregation in a concentration-dependent manner and suppressed clot formation. On the other hand, UDP exhibited distinct effects on whole blood or PRP in thromboelastogram. These data suggest that the difference on effects of UTP and UDP might have arisen from the different receptors that they stimulate and warrant further investigation with regard to their in vivo actions on platelet aggregation and hemostasis.

Discovery of a Series of 5-Amide-1H-pyrazole-3-carboxyl Derivatives as Potent P2Y14R Antagonists with Anti-Inflammatory Characters

UDPG/P2Y₁₄R signaling pathway has been considered as a potential therapeutic target for innate immune system diseases. Based on the scaffold hopping strategy, a series of pyrazole analogues were designed and synthesized as novel P2Y₁₄R antagonists with improved physicochemical properties, together with potential anti-inflammatory activities. Additionally, we designed and synthesized a fluorescent probe based on highly selective and potent PPTN to study the affinity of synthesized compounds. The optimized compound 16 (1-(4-fluorobenzyl)-5-(4-methylbenzamido)-1H-pyrazole-3-carboxylic acid, P2Y₁₄R IC₅₀ = 1.93 nM) showed strong binding ability to P2Y₁₄R, high selectivity, notably improved solubility, and more favorable pharmacokinetic profiles. Moreover, compound 16 possessed extremely low cytotoxicity and anti-inflammatory effect in vitro. In an acute peritonitis model, compound 16 could effectively reduce the levels of inflammatory factor IL-6, IL-1β, and TNF-α of mice induced by LPS. Compound 16, with potent in vitro and in vivo efficacy and favorable druggability, can be a promising candidate for further research.

Physiologic roles of P2 receptors in leukocytes

Since their discovery in the 1970s, purinergic receptors have been shown to play key roles in a wide variety of biologic systems and cell types. In the immune system, purinergic receptors participate in innate immunity and in the modulation of the adaptive immune response. In particular, P2 receptors, which respond to extracellular nucleotides, are widely expressed on leukocytes, causing the release of cytokines and chemokines and the formation of inflammatory mediators, and inducing phagocytosis, degranulation, and cell death. The activity of these receptors is regulated by ectonucleotidases-expressed in these same cell types-which regulate the availability of nucleotides in the extracellular environment. In this article, we review the characteristics of the main purinergic receptor subtypes present in the immune system, focusing on the P2 family. In addition, we describe the physiologic roles of the P2 receptors already identified in leukocytes and how they can positively or negatively modulate the development of infectious diseases, inflammation, and pain.

Purinergic receptors modulators: An emerging pharmacological tool for disease management

Purinergic signaling is mediated through extracellular nucleotides (adenosine 5'-triphosphate, uridine-5'-triphosphate, adenosine diphosphate, uridine-5'-diphosphate, and adenosine) that serve as signaling molecules. In the early 1990s, purines and pyrimidine receptors were cloned and characterized drawing the attention of scientists toward this aspect of cellular signaling. This signaling pathway is comprised of four subtypes of adenosine receptors (P1), eight subtypes of G-coupled protein receptors (P2YRs), and seven subtypes of ligand-gated ionotropic receptors (P2XRs). In current studies, the pathophysiology and therapeutic potentials of these receptors have been focused on. Various ligands, modulating the functions of purinergic receptors, are in current clinical practices for the treatment of various neurodegenerative disorders and cardiovascular diseases. Moreover, several purinergic receptors ligands are in advanced phases of clinical trials as a remedy for depression, epilepsy, autism, osteoporosis, atherosclerosis, myocardial infarction, diabetes, irritable bowel syndrome, and cancers. In the present study, agonists and antagonists of purinergic receptors have been summarized that may serve as pharmacological tools for drug design and development.

Naringin Relieves Diabetic Cardiac Autonomic Neuropathy Mediated by P2Y14 Receptor in Superior Cervical Ganglion

Diabetes mellitus (DM), an emerging chronic epidemic, contributes to mortality and morbidity around the world. Diabetic cardiac autonomic neuropathy (DCAN) is one of the most common complications associated with DM. Previous studies have shown that satellite glial cells (SGCs) in the superior cervical ganglia (SCG) play an indispensable role in DCAN progression. In addition, it has been shown that purinergic neurotransmitters, as well as metabotropic GPCRs, are involved in the pathophysiological process of DCAN. Furthermore, one traditional Chinese medicine, naringin may potently alleviate the effects of DCAN. Ferroptosis may be involved in DCAN progression. However, the role of naringin in DCAN as well as its detailed mechanism requires further investigation. In this research, we attempted to identify the effect and relevant mechanism of naringin in DCAN mitigation. We observed that compared with those of normal subjects, there were significantly elevated expression levels of P2Y₁₄ and IL-1β in diabetic rats, both of which were remarkably diminished by treatment with either P2Y₁₄ shRNA or naringin. In addition, abnormalities in blood pressure (BP), heart rate (HR), heart rate variability (HRV), sympathetic nerve discharge (SND), and cardiac structure in the diabetic model can also be partially returned to normal through the use of those treatments. Furthermore, a reduced expression of NRF2 and GPX4, as well as an elevated level of ROS, were detected in diabetic cases, which can also be improved with those treatments. Our results showed that naringin can effectively relieve DCAN mediated by the P2Y₁₄ receptor of SGCs in the SCG. Moreover, the NRF2/GPX4 pathway involved in ferroptosis may become one of the principal mechanisms participating in DCAN progression, which can be modulated by P2Y₁₄-targeted naringin and thus relieve DCAN. Hopefully, our research can supply one novel therapeutic target and provide a brilliant perspective for the treatment of DCAN.

GPR105-Targeted Therapy Promotes Gout Resolution as a Switch Between NETosis and Apoptosis of Neutrophils

The fate of infiltrating neutrophils in inflamed joints determines the development of acute gouty arthritis (AGA). GPR105 highly expressed in human neutrophils is sensitive to monosodium urate crystals (MSU); nevertheless, the roles of GPR105 in AGA remain unclear. Here, we show that GPR105 is significantly upregulated in peripheral polymorphonuclear neutrophils of AGA patients. GPR105 knockout (GPR105^−/−) prevented NETosis and induced apoptosis of neutrophils under MSU exposure, as well as attenuating inflammatory cascades in AGA. Mechanistically, GPR105 deletion activated cAMP-PKA signals, thereby disrupting Raf-Mek1/2-Erk1/2 pathway-mediated NADPH oxidase activation, contributing to inhibition of NETosis. Whereas, cAMP-PKA activation resulting in GPR105 deficiency modulated PI3K-Akt pathway to regulate apoptosis. More importantly, suppression of cAMP-PKA pathway by SQ22536 and H-89 restored NETosis instead of apoptosis in GPR105^−/− neutrophils, promoting MSU-induced gout flares. Interestingly, lobetyolin was screened out as a potent GPR105 antagonist using molecular docking-based virtual screening and in vitro activity test, which efficiently attenuated MSU-induced inflammatory response interacting with GPR105. Taken together, our study implicated that modulating cell death patterns between NETosis and apoptosis through targeting GPR105 could be a potential therapeutic strategy for the treatment of AGA.

Pannexin Channel Regulation of Cell Migration: Focus on Immune Cells

The role of Pannexin (PANX) channels during collective and single cell migration is increasingly recognized. Amongst many functions that are relevant to cell migration, here we focus on the role of PANX-mediated adenine nucleotide release and associated autocrine and paracrine signaling. We also summarize the contribution of PANXs with the cytoskeleton, which is also key regulator of cell migration. PANXs, as mechanosensitive ATP releasing channels, provide a unique link between cell migration and purinergic communication. The functional association with several purinergic receptors, together with a plethora of signals that modulate their opening, allows PANX channels to integrate physical and chemical cues during inflammation. Ubiquitously expressed in almost all immune cells, PANX1 opening has been reported in different immunological contexts. Immune activation is the epitome coordination between cell communication and migration, as leukocytes (i.e., T cells, dendritic cells) exchange information while migrating towards the injury site. In the current review, we summarized the contribution of PANX channels during immune cell migration and recruitment; although we also compile the available evidence for non-immune cells (including fibroblasts, keratinocytes, astrocytes, and cancer cells). Finally, we discuss the current evidence of PANX1 and PANX3 channels as a both positive and/or negative regulator in different inflammatory conditions, proposing a general mechanism of these channels contribution during cell migration.

Bridged Piperidine Analogues of a High Affinity Naphthalene-Based P2Y14R Antagonist

High affinity phenyl-piperidine P2Y₁₄R antagonist 1 (PPTN) was modified with piperidine bridging moieties to probe receptor affinity and hydrophobicity. Various 2-azanorbornane, nortropane, isonortropane, isoquinuclidine, and ring-opened cyclopentylamino derivatives preserved human P2Y₁₄R affinity (fluorescence binding assay), and their pharmacophoric overlay was compared. Enantiomeric 2-azabicyclo[2.2.1]hept-5-en-3-one precursors assured stereochemically unambiguous, diverse products. Pure (S,S,S) 2-azanorbornane enantiomer 15 (MRS4738) displayed higher affinity than 1 (3-fold higher affinity than enantiomer 16) and in vivo antihyperallodynic and antiasthmatic activity. Its double prodrug 143 (MRS4815) dramatically reduced lung inflammation in a mouse asthma model. Related lactams 21-24 and dicarboxylate 42 displayed intermediate affinity and enhanced aqueous solubility. Isoquinuclidine 34 (IC₅₀ 15.6 nM) and isonortropanol 30 (IC₅₀ 21.3 nM) had lower lipophilicity than 1. In general, rigidified piperidine derivatives did not lower lipophilicity dramatically, except those rings with multiple polar groups. P2Y₁₄R molecular modeling based on a P2Y₁₂R structure showed stable and persistent key interactions for compound 15.

A novel definition and treatment of hyperinflammation in COVID-19 based on purinergic signalling

Hyperinflammation plays an important role in severe and critical COVID-19. Using inconsistent criteria, many researchers define hyperinflammation as a form of very severe inflammation with cytokine storm. Therefore, COVID-19 patients are treated with anti-inflammatory drugs. These drugs appear to be less efficacious than expected and are sometimes accompanied by serious adverse effects. SARS-CoV-2 promotes cellular ATP release. Increased levels of extracellular ATP activate the purinergic receptors of the immune cells initiating the physiologic pro-inflammatory immune response. Persisting viral infection drives the ATP release even further leading to the activation of the P2X7 purinergic receptors (P2X7Rs) and a severe yet physiologic inflammation. Disease progression promotes prolonged vigorous activation of the P2X7R causing cell death and uncontrolled ATP release leading to cytokine storm and desensitisation of all other purinergic receptors of the immune cells. This results in immune paralysis with co-infections or secondary infections. We refer to this pathologic condition as hyperinflammation. The readily available and affordable P2X7R antagonist lidocaine can abrogate hyperinflammation and restore the normal immune function. The issue is that the half-maximal effective concentration for P2X7R inhibition of lidocaine is much higher than the maximal tolerable plasma concentration where adverse effects start to develop. To overcome this, we selectively inhibit the P2X7Rs of the immune cells of the lymphatic system inducing clonal expansion of Tregs in local lymph nodes. Subsequently, these Tregs migrate throughout the body exerting anti-inflammatory activities suppressing systemic and (distant) local hyperinflammation. We illustrate this with six critically ill COVID-19 patients treated with lidocaine.

Microglial P2Y14 receptor contributes to central sensitization following repeated inflammatory dural stimulation

BACKGROUND

Recent studies have indicated that P2Y receptors in spinal microglia play a role in the development of neuropathic and inflammatory pain. However, it remains unclear whether P2Y receptors in microglia are involved in the pathogenesis of migraine. Therefore, the aim of this study was to investigate the role of microglial P2Y14 receptor in trigeminal cervical complex (TCC) in migraine.

METHODS

We used a rat model of migraine induced by repeated inflammatory stimulation of the dura and examined the expression of P2Y14 receptor in the TCC in migraine rats by Western Blotting and immunofluorescence staining. Then, we determined the effect of P2Y14 antagonist PPTN on inflammatory soup (IS)-induced mechanical allodynia, microglial activation and ERK expression in TCC.

RESULTS

The expression level of P2Y14 receptor increased significantly in microglia in TCC after 4 or 7 days of repeated IS stimulation of the dura. Application of PPTN significantly attenuated the decrease of periorbital pain threshold in migraine model rats. In addition, repeated IS stimulation of the dura induced the activation of microglia and the phosphorylation of the ERK1/2 in microglia in TCC, which were abolished by the application of PPTN.

CONCLUSION

Our findings suggest that the increased P2Y14 receptor in microglia in TCC play a crucial role in the generation of mechanical allodynia in migraine rat model. Furthermore, the activation of the P2Y14 receptor is involved in microglial activation and ERK phosphorylation as well. The P2Y14 receptor in microglia might be used as a potential target for migraine treatment.

Recommended tool compounds and drugs for blocking P2X and P2Y receptors

This review article presents a collection of tool compounds that selectively block and are recommended for studying P2Y and P2X receptor subtypes, investigating their roles in physiology and validating them as future drug targets. Moreover, drug candidates and approved drugs for P2 receptors will be discussed.

P2RY14 Is a Potential Biomarker of Tumor Microenvironment Immunomodulation and Favorable Prognosis in Patients With Head and Neck Cancer

The tumor microenvironment (TME) has a crucial role in tumor development, progression, and treatment response. Yet, the exact interaction between cancer biology and the TME is not fully understood. The following study analyzed the correlation between immune/stromal/estimate scores and survival prognosis in head and neck squamous cell carcinoma (HNSC) using a bioinformatic method. As a result, a predictive biomarker, UDP-glucose-specific G(i) protein-coupled P2Y receptor (P2RY14), was discovered. The potential role of P2RY14-driven signaling pathways in the immune-remodeling of TME was then investigated. Briefly, low immune scores were associated with unfavorable prognosis and clinical-stage, larger tumor size, and the down-regulation of P2RY14 in HNSC patients. In addition, the survival analysis showed that HNSC patients with high expression had longer survival than patients with low expression from both TCGA databases and our own patients. We further discovered that P2RY14 is involved in the immune activity in the TME of HNSC; a downregulation of P2RY14 resulted in being an indicator for the conversion of TME status (from immune-dominant to metabolic-dominant status). The intersection analysis of genes co-expressed with P2RY14 indicated that the T-cell receptor signaling pathway and PD-L1 expression and PD-1 checkpoint pathway were candidate signaling pathways driven by the P2RY14 gene in HNSC. Further investigation of immune-associated signaling pathways regulated by P2RY14 may help HNSC patients gain higher immunotherapy benefits.

Novel Non-Opioid Based Therapeutics for Chronic Neuropathic Pain

Chronic neuropathic pain is currently a major health issue in U.S. complicated by the lack of non-opioid analgesic alternatives. Our investigations led to the discovery of major signaling pathways involved in the transition of acute to chronic neuropathic pain and the identification of several targets for therapeutic intervention. Our translational approach has facilitated the advancement of novel medicines for chronic neuropathic pain that are in advanced clinical development and clinical trials.

Adipocyte P2Y14 receptors play a key role in regulating whole-body glucose and lipid homeostasis

Obesity is the major driver of the worldwide epidemic in type 2 diabetes (T2D). In the obese state, chronically elevated plasma free fatty acid levels contribute to peripheral insulin resistance, which can ultimately lead to the development of T2D. For this reason, drugs that are able to regulate lipolytic processes in adipocytes are predicted to have considerable therapeutic potential. Gi-coupled P2Y14 receptor (P2Y14R; endogenous agonist, UDP-glucose) is abundantly expressed in both mouse and human adipocytes. Because activated Gi-type G proteins exert an antilipolytic effect, we explored the potential physiological relevance of adipocyte P2Y14Rs in regulating lipid and glucose homeostasis. Metabolic studies indicate that the lack of adipocyte P2Y14R enhanced lipolysis only in the fasting state, decreased body weight, and improved glucose tolerance and insulin sensitivity. Mechanistic studies suggested that adipocyte P2Y14R inhibits lipolysis by reducing lipolytic enzyme activity, including ATGL and HSL. In agreement with these findings, agonist treatment of control mice with a P2Y14R agonist decreased lipolysis, an effect that was sensitive to inhibition by a P2Y14R antagonist. In conclusion, we demonstrate that adipose P2Y14Rs were critical regulators of whole-body glucose and lipid homeostasis, suggesting that P2Y14R antagonists might be beneficial for the therapy of obesity and T2D.

Structure-Activity Relationship of Heterocyclic P2Y14 Receptor Antagonists: Removal of the Zwitterionic Character with Piperidine Bioisosteres

A known zwitterionic, heterocyclic P2Y14R antagonist 3a was substituted with diverse groups on the central phenyl and terminal piperidine moieties, following a computational selection process. The most potent analogues contained an uncharged piperidine bioisostere, prescreened in silico, while an aza-scan (central phenyl ring) reduced P2Y14R affinity. Piperidine amide 11, 3-aminopropynyl 19, and 5-(hydroxymethyl)isoxazol-3-yl) 29 congeners in the triazole series maintained moderate receptor affinity. Adaption of 5-(hydroxymethyl)isoxazol-3-yl gave the most potent naphthalene-containing (32; MRS4654; IC50, 15 nM) and less active phenylamide-containing (33) scaffolds. Thus, a zwitterion was nonessential for receptor binding, and molecular docking and dynamics probed the hydroxymethylisoxazole interaction with extracellular loops. Also, amidomethyl ester prodrugs were explored to reversibly block the conserved carboxylate group to provide neutral analogues, which were cleavable by liver esterase, and in vivo efficacy demonstrated. We have, in stages, converted zwitterionic antagonists into neutral molecules designed to produce potent P2Y14R antagonists for in vivo application.

UDP-glucose and P2Y14 receptor amplify allergen-induced airway eosinophilia

Airway eosinophilia is a hallmark of allergic asthma and is associated with mucus production, airway hyperresponsiveness, and shortness of breath. Although glucocorticoids are widely used to treat asthma, their prolonged use is associated with several side effects. Furthermore, many individuals with eosinophilic asthma are resistant to glucocorticoid treatment, and they have an unmet need for novel therapies. Here, we show that UDP-glucose (UDP-G), a nucleotide sugar, is selectively released into the airways of allergen-sensitized mice upon their subsequent challenge with that same allergen. Mice lacking P2Y14R, the receptor for UDP-G, had decreased airway eosinophilia and airway hyperresponsiveness compared with wild-type mice in a protease-mediated model of asthma. P2Y14R was dispensable for allergic sensitization and for the production of type 2 cytokines in the lung after challenge. However, UDP-G increased chemokinesis in eosinophils and enhanced their response to the eosinophil chemoattractant, CCL24. In turn, eosinophils triggered the release of UDP-G into the airway, thereby amplifying eosinophilic recruitment. This positive feedback loop was sensitive to therapeutic intervention, as a small molecule antagonist of P2Y14R inhibited airway eosinophilia. These findings thus reveal a pathway that can be therapeutically targeted to treat asthma exacerbations and glucocorticoid-resistant forms of this disease.

Design, synthesis and evaluation of 3-amide-5-aryl benzoic acid derivatives as novel P2Y14R antagonists with potential high efficiency against acute gouty arthritis

P2Y₁₄ nucleotide receptor plays important roles in series of physiological and pathologic events especially associated with immune and inflammation. Based on the 3-amide benzoic acid scaffold reported by our group previously, a series of 5-aryl-3-amide benzoic acid derivatives were designed as novel P2Y₁₄ antagonists with improved pharmacokinetic properties. Among which compound 11m showed most potent P2Y₁₄ antagonizing activity with an IC₅₀ value of 2.18 nM, furnishing greatly improved water solubility and bioavailability compared with PPTN. In MSU-induced acute gouty arthritis model in mice, 11m exerted promising in vivo efficacy in alleviating mice paw swelling and inflammatory infiltration. Mechanistically, compound 11m notably blocked pyroptosis of macrophages through inhibiting NLRP3 inflammasome activation. This work may contribute to the identification of potential therapeutic agents to intervene in acute gouty arthritis.

P2Y14 Receptor as a Target for Neutrophilia Attenuation in Severe COVID-19 Cases: From Hematopoietic Stem Cell Recruitment and Chemotaxis to Thrombo-inflammation

The global SARS-CoV-2 pandemic starting in 2019 has already reached more than 2.3 million deaths. Despite the scientific community’s efforts to investigate the COVID-19 disease, a drug for effectively treating or curing patients yet needs to be discovered. Hematopoietic stem cells (HSC) differentiating into immune cells for defense express COVID-19 entry receptors, and COVID-19 infection hinders their differentiation. The importance of purinergic signaling in HSC differentiation and innate immunity has been recognized. The metabotropic P2Y14 receptor subtype, activated by UDP-glucose, controls HSC differentiation and mobilization. Thereon, the exacerbated activation of blood immune cells amplifies the inflammatory state observed in COVID-19 patients, specially through the continuous release of reactive oxygen species and extracellular neutrophil traps (NETs). Further, the P2Y14 subtype, robustly inhibits the infiltration of neutrophils into various epithelial tissues, including lungs and kidneys. Here we discuss findings suggesting that antagonism of the P2Y14 receptor could prevent the progression of COVID-19-induced systemic inflammation, which often leads to severe illness and death cases. Considering the modulation of neutrophil recruitment of extreme relevance for respiratory distress and lung failure prevention, we propose that P2Y14 receptor inhibition by its selective antagonist PPTN could limit neutrophil recruitment and NETosis, hence limiting excessive formation of oxygen reactive species and proteolytic activation of the kallikrein-kinin system and subsequent bradykinin storm in the alveolar septa of COVID-19 patients.

That was then, this is now: the development of our knowledge and understanding of P2 receptor subtypes

P2 receptors are present in virtually all tissues and cell types in the human body, and they mediate the physiological and pharmacological actions of extracellular purine and pyrimidine nucleotides. They were first characterised and named by Geoff Burnstock in 1978, then subdivided into P_2X and P_2Y purinoceptors in 1985 on the basis of pharmacological criteria in functional studies on native receptors. Molecular cloning of receptors in the 1990s revealed P2X receptors to comprise seven different subunits that interact to produce functional homo- and heterotrimeric ligand-gated cation channels. A family of eight P2Y G protein–coupled receptors were also cloned, which can form homo- and heterodimers. Deep insight into the molecular mechanisms of agonist and antagonist action has been provided by more recent determination of the tertiary and quaternary structures of several P2X and P2Y receptor subtypes. Agonists and antagonists that are highly selective for individual subtypes are now available and some are in clinical use. This has all come about because of the intelligence, insight and drive of the force of nature that was Geoff Burnstock.

The P2Y/P2X divide: How it began

Extracellular purine and pyrimidine nucleotides produce their pharmacological effects through P2 receptors. These were first named by Geoff Burnstock in an extensive review in 1978. They were then subdivided into P_2X and P_2Y purinoceptors by Burnstock and Kennedy in 1985, based on applying pharmacological criteria to data generated by functional studies in smooth muscle tissues. Several other P2 subtypes, P_2T, P_2Z, P_2U and P_2D were subsequently identified in the following years, again using pharmacological criteria. The number and identity of subtypes were clarified and simplified by the cloning of seven ATP-sensitive ligand-gated ion channel subunits and eight adenine and/or uracil nucleotide-sensitive G protein-coupled receptors from 1993 onwards. The former were all classified as members of the P2X receptor family and the latter as members of the P2Y receptor family. More recently, high resolution imaging of the tertiary and quaternary structures of several P2X and P2Y receptor subtypes has provided a much greater understanding of how and where agonists and antagonists bind to the receptors and how this leads to changes in receptor conformation and activity. In addition, medicinal chemistry has produced a variety of subtype-selective agonists and antagonists, some of which are now in clinical use. This progress and success is a testimony to the foresight, intelligence, enthusiasm and drive of Geoff Burnstock, who led the field forward throughout his scientific life.

Molecular pharmacology of P2Y receptor subtypes

Professor Geoffrey Burnstock proposed the concept of purinergic signaling via P1 and P2 receptors. P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular adenine and uracil nucleotides. Eight mammalian P2Y receptor subtypes have been identified. They are divided into two subgroups (P2Y₁, P2Y₂, P2Y₄, P2Y₆, and P2Y₁₁) and (P2Y₁₂, P2Y₁₃, and P2Y₁₄). P2Y receptors are found in almost all cells and mediate responses in physiology and pathophysiology including pain and inflammation. The antagonism of platelet P2Y₁₂ receptors by cangrelor, ticagrelor or active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel reduces the ADP-induced platelet aggregation in patients with thrombotic complications of vascular diseases. The nucleotide agonist diquafosol acting at P2Y₂ receptors is used for the treatment of the dry eye syndrome. Structural information obtained by crystallography of the human P2Y₁ and P2Y₁₂ receptor proteins, site-directed mutagenesis and molecular modeling will facilitate the rational design of novel selective drugs.

UDP-glucose, a cellular danger signal, and nucleotide receptor P2Y14 enhance the invasion of human extravillous trophoblast cells

INTRODUCTION

P2Y14, one of the P2Y purinergic G-protein coupled receptors, is expressed in a variety of cells and tissues. Its ligand, UDP-glucose (UDPG), is released from damaged and stress-stimulated cells and acts as a danger signal via P2Y14. Thus, P2Y14 plays an important role in immunological defense systems. Here, we aimed to elucidate the expression, localization, and role of P2Y14 in human trophoblasts and the placenta.

METHODS

Human chorionic villus and placental tissues were subjected to immunostaining for P2Y14 protein and an extravillous trophoblast (EVT) marker, HLA-G. We examined the expression of P2Y14 and the effect of UDPG on cell proliferation and invasion in an EVT cell line, HTR-8/SVneo, using an MTS assay and a Transwell assay, respectively. We tested the effect of UDPG on cell invasion in P2Y14-underexpressing HTR-8/SVneo clones established by the lentiviral introduction of shRNA for P2RY14 mRNA.

RESULTS

Immunostaining revealed that P2Y14 was exclusively expressed by EVTs. P2RY14 mRNA and P2Y14 protein were expressed in HTR-8/SVneo cells. UDPG did not affect cell proliferation but it did enhance invasion. Inhibition of P2Y14 and decreasing the expression of P2Y14 suppressed UDPG-mediated invasive activity.

CONCLUSIONS

These results showed that EVT selectively expressed P2Y14 and that P2Y14 was positively involved in UDPG-enhanced EVT invasion. It suggests the possible existence of a danger signal-mediated physiological system at the fetomaternal interface where UDPG released from maternal tissues through destruction by EVT invasion may accelerate EVT invasion, allowing EVTs to undergo successful placentation and vascular remodeling.

Exploration of Alternative Scaffolds for P2Y14 Receptor Antagonists Containing a Biaryl Core

Various heteroaryl and bicyclo-aliphatic analogues of zwitterionic biaryl P2Y₁₄ receptor (P2Y₁₄R) antagonists were synthesized, and affinity was measured in P2Y₁₄R-expressing Chinese hamster ovary cells by flow cytometry. Given this series' low water solubility, various polyethylene glycol derivatives of the distally binding piperidin-4-yl moiety of moderate affinity were synthesized. Rotation of previously identified 1,2,3-triazole attached to the central m-benzoic acid core (25) provided moderate affinity but not indole and benzimidazole substitution of the aryl-triazole. The corresponding P2Y₁₄R region is predicted by homology modeling as a deep, sterically limited hydrophobic pocket, with the outward pointing piperidine moiety being the most flexible. Bicyclic-substituted piperidine ring derivatives of naphthalene antagonist 1, e.g., quinuclidine 17 (MRS4608, IC₅₀ ≈ 20 nM at hP2Y₁₄R/mP2Y₁₄R), or of triazole 2, preserved affinity. Potent antagonists 1, 7a, 17, and 23 (10 mg/kg) protected in an ovalbumin/Aspergillus mouse asthma model, and PEG conjugate 12 reduced chronic pain. Thus, we expanded P2Y₁₄R antagonist structure-activity relationship, introducing diverse physical-chemical properties.

Potential Therapeutic Applications of P2 Receptor Antagonists: From Bench to Clinical Trials

BACKGROUND

Extracellular purines and pyrimidines have important physiological functions in mammals. Purines and pyrimidines act on P1 and P2 purinergic receptors, which are widely expressed in the plasma membrane in various cell types. P2 receptors act as important therapeutic targets and are associated with several disorders, such as pain, neurodegeneration, cancer, inflammation, and thrombosis. However, the use of antagonists for P2 receptors in clinical therapy, with the exception of P2Y12, is a great challenge. Currently, many research groups and pharmaceutical companies are working on the development of specific antagonist molecules for each receptor subtype that could be used as new medicines to treat their respective disorders.

OBJECTIVE

The present review compiles some interesting findings on the application of P2 receptor antagonists in different in vitro and in vivo experimental models as well as the progress of advanced clinical trials with these compounds.

CONCLUSION

Despite all of the exciting results obtained on the bench, few antagonists of P2 receptors advanced to the clinical trials, and once they reach this stage, the effectiveness of the therapy is not guaranteed, as in the example of P2X7 antagonists. Despite this, P2Y12 receptor antagonists have a history of success and have been used in therapy for at least two decades to prevent thrombosis in patients at risk for myocardial infarctions. This breakthrough is the motivation for scientists to develop new drugs with antagonistic activity for the other P2 receptors; thus, in a matter of years, we will have an evolution in the field of purinergic therapy.

Proinflammatory P2Y14 receptor inhibition protects against ischemic acute kidney injury in mice

Ischemic acute kidney injury (AKI), a complication that frequently occurs in hospital settings, is often associated with hemodynamic compromise, sepsis, cardiac surgery, or exposure to nephrotoxins. Here, using a murine renal ischemia/reperfusion injury (IRI) model, we show that intercalated cells (ICs) rapidly adopted a proinflammatory phenotype after IRI. Wwe demonstrate that during the early phase of AKI either blockade of the proinflammatory P2Y14 receptor located on the apical membrane of ICs or ablation of the gene encoding the P2Y14 receptor in ICs (a) inhibited IRI-induced increase of chemokine expression in ICs, (b) reduced neutrophil and monocyte renal infiltration, (c) reduced the extent of kidney dysfunction, and (d) attenuated proximal tubule damage. These observations indicate that the P2Y14 receptor participates in the very first inflammatory steps associated with ischemic AKI. In addition, we show that the concentration of the P2Y14 receptor ligand UDP-glucose (UDP-Glc) was higher in urine samples from intensive care unit patients who developed AKI compared with patients without AKI. In particular, we observed a strong correlation between UDP-Glc concentration and the development of AKI in cardiac surgery patients. Our study identifies the UDP-Glc/P2Y14 receptor axis as a potential target for the prevention and/or attenuation of ischemic AKI.

P2Y14 Receptor Antagonists Reverse Chronic Neuropathic Pain in a Mouse Model

Eight P2Y₁₄R antagonists, including three newly synthesized analogues, containing a naphthalene or phenyl-triazolyl scaffold were compared in a mouse model of chronic neuropathic pain (sciatic constriction). P2Y₁₄R antagonists rapidly (≤30 min) reversed mechano-allodynia, with maximal effects typically within 1 h after injection. Two analogues (4-[4-(4-piperidinyl)phenyl]-7-[4-(trifluoromethyl)phenyl]-2-naphthalenecarboxylic acid 1 and N-acetyl analogue 4, 10 μmol/kg, i.p.) achieved complete pain reversal (100%) at 1 to 2 h, with relief evident up to 5 h for 4 (41%). A reversed triazole analogue 7 reached 87% maximal protection. Receptor affinity was determined using a fluorescent antagonist binding assay, indicating similar mouse and human P2Y₁₄R affinity. The mP2Y₁₄R affinity was only partially predictive of in vivo efficacy, suggesting the influence of pharmacokinetic factors. Thus P2Y₁₄R is a potential therapeutic target for treating chronic pain.

Role of UDP-Sugar Receptor P2Y14 in Murine Osteoblasts

The purinergic (P2) receptor P2Y₁₄ is the only P2 receptor that is stimulated by uridine diphosphate (UDP)-sugars and its role in bone formation is unknown. We confirmed P2Y₁₄ expression in primary murine osteoblasts (CB-Ob) and the C2C12-BMP2 osteoblastic cell line (C2-Ob). UDP-glucose (UDPG) had undiscernible effects on cAMP levels, however, induced dose-dependent elevations in the cytosolic free calcium concentration ([Ca²⁺]_i) in CB-Ob, but not C2-Ob cells. To antagonize the P2Y₁₄ function, we used the P2Y₁₄ inhibitor PPTN or generated CRISPR-Cas9-mediated P2Y₁₄ knockout C2-Ob clones (Y14_KO). P2Y₁₄ inhibition facilitated calcium signalling and altered basal cAMP levels in both models of osteoblasts. Importantly, P2Y₁₄ inhibition augmented Ca²⁺ signalling in response to ATP, ADP and mechanical stimulation. P2Y₁₄ knockout or inhibition reduced osteoblast proliferation and decreased ERK1/2 phosphorylation and increased AMPKα phosphorylation. During in vitro osteogenic differentiation, P2Y₁₄ inhibition modulated the timing of osteogenic gene expression, collagen deposition, and mineralization, but did not significantly affect differentiation status by day 28. Of interest, while P2ry14^-/- mice from the International Mouse Phenotyping Consortium were similar to wild-type controls in bone mineral density, their tibia length was significantly increased. We conclude that P2Y₁₄ in osteoblasts reduces cell responsiveness to mechanical stimulation and mechanotransductive signalling and modulates osteoblast differentiation.

Update of P2Y receptor pharmacology: IUPHAR Review 27

Eight G protein-coupled P2Y receptor subtypes respond to extracellular adenine and uracil mononucleotides and dinucleotides. P2Y receptors belong to the δ group of rhodopsin-like GPCRs and contain two structurally distinct subfamilies: P2Y₁ , P2Y₂ , P2Y₄ , P2Y₆ , and P2Y₁₁ (principally G_q protein-coupled P2Y₁ -like) and P2Y_12-14 (principally G_i protein-coupled P2Y₁₂ -like) receptors. Brain P2Y receptors occur in neurons, glial cells, and vasculature. Endothelial P2Y₁ , P2Y₂ , P2Y₄ , and P2Y₆ receptors induce vasodilation, while smooth muscle P2Y₂ , P2Y₄ , and P2Y₆ receptor activation leads to vasoconstriction. Pancreatic P2Y₁ and P2Y₆ receptors stimulate while P2Y₁₃ receptors inhibits insulin secretion. Antagonists of P2Y₁₂ receptors, and potentially P2Y₁ receptors, are anti-thrombotic agents, and a P2Y₂ /P2Y₄ receptor agonist treats dry eye syndrome in Asia. P2Y receptor agonists are generally pro-inflammatory, and antagonists may eventually treat inflammatory conditions. This article reviews recent developments in P2Y receptor pharmacology (using synthetic agonists and antagonists), structure and biophysical properties (using X-ray crystallography, mutagenesis and modelling), physiological and pathophysiological roles, and present and potentially future therapeutic targeting.

Analysis of purine receptor expression and functionality in alveolar epithelial cells

Despite its fundamental role in providing an extensive surface for gas exchange, the alveolar epithelium (AE) serves as an immunological barrier through, e.g., the release of proinflammatory cytokines and secretion of surfactant to prevent alveolar collapse. Thus, AE is important for sustaining lung homeostasis. Extracellular ATP secreted by alveolar epithelial cells (AECs) is involved in physiological and pathological conditions and acts mainly through the activation of purine receptors (P2Rs). When studying P2R-mediated processes, primary isolated type II AECs (piAECs) still represent the gold standard in in vitro research, although their preparation is time-consuming and requires the sacrifice of many animals. Hence, cultivated immortalized and tumor-derived AEC lines may constitute a valuable alternative. In this work, we examined P2R expression and functionality in piAECs, in immortalized and tumor-derived AEC lines with the purpose of gaining a better understanding of purinergic signaling in different cell systems and assisting researchers in the choice of a suitable cell line with a certain P2R in demand. We combined mRNA and protein analysis to evaluate the expression of P2R. For pharmacological testing, we conducted calcium ([Ca²⁺]) measurements and siRNA receptor knockdown. Interestingly, the mRNA and protein levels of P2Y₂, P2Y_6, and P2X₄ were detected on all cell lines. Concerning functionality, P2XR could be narrowed to L2 and piAECs while P2YR were active in all cell lines.

Discovery of novel and potent P2Y14R antagonists via structure-based virtual screening for the treatment of acute gouty arthritis

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A reliable Glide docking-based virtual screening (VS) pipeline for P2Y₁₄R was developed.

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Several potent P2Y₁₄R antagonists with novel scaffolds were identified utilizing the VS strategy.

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P2Y₁₄R inhibitory effect was evaluated by testing cAMP levels in HEK293 cells.

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Anti-gout activity of screened compound was detected in MSU-treated THP-1 cells.

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The mechanism of test compound in treating acute gouty arthritis was elucidated.

P2Y₁₄ nucleotide receptor is a Gi protein-coupled receptor, which is widely involved in physiological and pathologic events. Although several P2Y₁₄R antagonists have been developed thus far, few have successfully been developed into a therapeutic drug. In this study, on the basis of two P2Y₁₄R homology models, Glide docking-based virtual screening (VS) strategy was employed for finding potent P2Y₁₄R antagonists with novel chemical architectures. A total of 19 structurally diverse compounds identified by VS and drug-like properties testing were set to experimental testing. 10 of them showed good inhibitory effects against the P2Y₁₄R (IC₅₀ < 50 nM), including four compounds (compounds 8, 10, 18 and 19) with IC₅₀ value below 10 nM. The best VS hit, compound 8 exhibited the best antagonistic activity, with IC₅₀ value of 2.46 nM. More importantly, compound 8 restrained monosodium uric acid (MSU)-induced pyroptosis of THP-1 cells through blocking the activation of Nod-like receptor 3 (NLRP3) inflammasome, which was attributed to its inhibitory effects on P2Y₁₄R-cAMP pathways. The key favorable residues uncovered using MM/GBSA binding free energy calculations/decompositions were detected and discussed. These findings suggest that the compound 8 can be used as a good lead compound for further optimization to obtain more promising P2Y₁₄R antagonists for the treatment of acute gouty arthritis.

The P2Y14 receptor in the trigeminal ganglion contributes to the maintenance of inflammatory pain

P2Y purinergic receptors expressed in neurons and satellite glial cells (SGCs) of the trigeminal ganglion (TG) contribute to inflammatory and neuropathic pain. P2Y₁₄ receptor expression is reported in the spinal cord, dorsal root ganglion (DRG), and TG. In present study, the role of P2Y₁₄ receptor in the TG in inflammatory orofacial pain of Sprague-Dawley (SD) rats was investigated. Peripheral injection of complete Freund's adjuvant (CFA) induced mechanical hyperalgesia with the rapid upregulation of P2Y₁₄ receptor, glial fibrillary acidic protein (GFAP), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), C-C chemokine CCL2, phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), and phosphorylated p38 (p-p38) proteins in the TG. Furthermore, immunofluorescence staining confirmed the CFA-induced upregulation of P2Y₁₄ receptor. Double immunostaining showed that P2Y₁₄ receptor colocalized with glutamine synthetase (GS) and neuronal nuclei (NeuN). Finally, trigeminal injection of a selective antagonist (PPTN) of P2Y₁₄ receptor attenuated CFA-induced mechanical hyperalgesia. PPTN also decreased the upregulation of the GFAP, IL-1β, TNF-α, CCL2, p-ERK1/2, and p-p38 proteins. Our findings showed that P2Y₁₄ receptor in TG may contribute to orofacial inflammatory pain via regulating SGCs activation, releasing cytokines (IL-1β, TNF-α, and CCL2), and phosphorylating ERK1/2 and p38.

Functional characterization of purinergic receptor P2Y14 in the Japanese flounder (Paralichthys olivaceus) head kidney macrophages

Extracellular nucleotides and nucleotide sugars are important danger-associated signaling molecules that play critical roles in regulation of immune responses in mammals through activation of purinergic receptors located on the cell surface. However, the immunological role of extracellular UDP-glucose-activated P2Y₁₄ receptor (P2Y₁₄R) in fish still remains unknown. In this study, we identified and characterized a P2Y₁₄R paralog in the Japanese flounder (Paralichthys olivaceus). The mRNA transcripts of P2Y₁₄R are detected in all examined Japanese flounder tissues. Compared with the UDP-activated P2Y₆ receptor, however, P2Y₁₄R gene is highly expressed in Japanese flounder head kidney macrophages (HKMs). In addition, P2Y₁₄R is significantly upregulated following inflammatory stimulation with LPS and poly (I:C) in the HKMs, suggesting a role of P2Y₁₄R in response to inflammation in fish. Furthermore, activation of P2Y₁₄ receptor with its potent and selective agonist MRS 2905 resulted in a decreased expression of LPS-induced pro-inflammatory cytokine IL-1beta gene in the HKMs. In contrast, inhibition of P2Y₁₄ receptor activity or down-regulation of the endogenous expression of P2Y₁₄R by small interfering RNA significantly upregulates the LPS-induced pro-inflammatory cytokine IL-1beta gene expression in the HKMs, demonstrating that P2Y₁₄R is involved in inflammation regulation in fish. Moreover, stimulation of the Japanese flounder HKMs with UDP-glucose evoked a rapid increase of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in a dose- and time-dependent manner, indicating the involvement of P2Y₁₄R in activation of ERK1/2 signaling in fish immune cells. Taken together, we demonstrated that the inducible P2Y₁₄R plays an important role in regulation of fish innate immunity.

Extracellular Nucleotides and P2 Receptors in Renal Function

The understanding of the nucleotide/P2 receptor system in the regulation of renal hemodynamics and transport function has grown exponentially over the last 20 yr. This review attempts to integrate the available data while also identifying areas of missing information. First, the determinants of nucleotide concentrations in the interstitial and tubular fluids of the kidney are described, including mechanisms of cellular release of nucleotides and their extracellular breakdown. Then the renal cell membrane expression of P2X and P2Y receptors is discussed in the context of their effects on renal vascular and tubular functions. Attention is paid to effects on the cortical vasculature and intraglomerular structures, autoregulation of renal blood flow, tubuloglomerular feedback, and the control of medullary blood flow. The role of the nucleotide/P2 receptor system in the autocrine/paracrine regulation of sodium and fluid transport in the tubular and collecting duct system is outlined together with its role in integrative sodium and fluid homeostasis and blood pressure control. The final section summarizes the rapidly growing evidence indicating a prominent role of the extracellular nucleotide/P2 receptor system in the pathophysiology of the kidney and aims to identify potential therapeutic opportunities, including hypertension, lithium-induced nephropathy, polycystic kidney disease, and kidney inflammation. We are only beginning to unravel the distinct physiological and pathophysiological influences of the extracellular nucleotide/P2 receptor system and the associated therapeutic perspectives.

Recent progress on the discovery of P2Y14 receptor antagonists

The P2Y₁₄ receptor (P2Y₁₄R), a G protein-coupled receptor (GPCR), is activated by extracellular nucleotides. P2Y₁₄R is involved in inflammatory, diabetes, immune processes and other related complications, and is therefore an attractive therapeutic target. As the three-dimensional structure of the P2Y₁₄R has not yet been elucidated, homology modeling based on the crystallography of the closely related P2Y₁₂R have been used in the structure-based design of P2Y₁₄R ligands. Several P2Y₁₄R antagonists with excellent potency and high subtype-selectivity have been discovered in recent years. In this review, development of novel small molecules as antagonists of P2Y₁₄R was described.

P2Y14 receptor is functionally expressed in satellite glial cells and mediates interleukin-1β and chemokine CCL2 secretion

Satellite glial cells (SGCs) activation in the trigeminal ganglia (TG) is critical in various abnormal orofacial sensation in nerve injury and inflammatory conditions. SGCs express several subtypes of P2 purinergic receptors contributing to the initiation and maintenance of neuropathic pain. The P2Y₁₄ receptor, a G-protein-coupled receptor activated by uridine diphosphate (UDP)-glucose and other UDP sugars, mediates various physiologic events such as immune, inflammation, and pain. However, the expression, distribution, and function of P2Y₁₄ receptor in SGCs remains largely unexplored. Our study reported the expression and functional identification of P2Y₁₄ receptor in SGCs. SGCs were isolated from TG of rat, and the P2Y₁₄ receptor expression was examined using immunofluorescence technique. Cell proliferation and viability were examined via cell counting kit-8 experiment. Immunofluorescence demonstrated the presence of P2Y₁₄ receptor in SGCs. Immunofluorescence and western blot showed that UDP-glucose treatment upregulated glial fibrillary acid protein, a common marker for glial activation. Extracellular UDP-glucose enhanced the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38, which were both abolished by the P2Y₁₄ receptor inhibitor (PPTN). Furthermore, quantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay demonstrated that extracellular UDP-glucose significantly enhanced interleukin-1β (IL-1β) and chemokine CCL2 (CCL2) release, which was abolished by PPTN and significantly decreased by inhibitors of MEK/ERK (U0126) and p38 (SB202190). Our findings directly proved the functional presence of P2Y₁₄ receptor in SGCs. It was also verified that P2Y₁₄ receptor activation was involved in activating SGCs, phosphorylating MAPKs, and promoting the secretion of IL-1β and CCL2 via ERK and p38 pathway.

Pharmacology of P2Y receptors

P2Y receptors are G-protein-coupled receptors (GPCRs) for extracellular nucleotides. There are eight mammalian P2Y receptor subtypes divided into two subgroups (P2Y₁, P2Y₂, P2Y₄, P2Y₆, and P2Y₁₁) and (P2Y₁₂, P2Y₁₃, and P2Y₁₄). The P2Y receptors are expressed in various cell types and play important roles in physiology and pathophysiology including inflammatory responses and neuropathic pain. The antagonism of P2Y₁₂ receptors is used in pharmacotherapy for the prevention and therapy of cardiovascular events. The nucleoside analogue ticagrelor and active metabolites of the thienopyridine compounds ticlopidine, clopidogrel and prasugrel inhibit platelet P2Y₁₂ receptors and reduce thereby platelet aggregation. The P2Y₂ receptor agonist diquafosol is used for the treatment of the dry eye syndrome. The P2Y receptor subtypes differ in their amino acid sequences, their pharmacological profiles and their signaling transduction pathways. Recently, selective receptor ligands have been developed for all subtypes. The published crystal structures of the human P2Y₁ and P2Y₁₂ receptors as well as receptor models will facilitate the development of novel drugs for pharmacotherapy.

Breakthrough in GPCR Crystallography and Its Impact on Computer-Aided Drug Design

Recent crystallographic structures of G protein-coupled receptors (GPCRs) have greatly advanced our understanding of the recognition of their diverse agonist and antagonist ligands. We illustrate here how this applies to A_2A adenosine receptors (ARs) and to P2Y₁ and P2Y₁₂ receptors (P2YRs) for ADP. These X-ray structures have impacted the medicinal chemistry aimed at discovering new ligands for these two receptor families, including receptors that have not yet been crystallized but are closely related to the known structures. In this Chapter, we discuss recent structure-based drug design projects that led to the discovery of: (a) novel A₃AR agonists based on a highly rigidified (N)-methanocarba scaffold for the treatment of chronic neuropathic pain and other conditions, (b) fluorescent probes of the ARs and P2Y₁₄R, as chemical tools for structural probing of these GPCRs and for improving assay capabilities, and (c) new more drug-like antagonists of the inflammation-related P2Y₁₄R. We also describe the computationally enabled molecular recognition of positive (for A₃AR) and negative (P2Y₁R) allosteric modulators that in some cases are shown to be consistent with structure-activity relationship (SAR) data. Thus, computational modeling has become an essential tool for the design of purine receptor ligands.

Structure-Guided Modification of Heterocyclic Antagonists of the P2Y14 Receptor

The P2Y14 receptor (P2Y14R) mediates inflammatory activity by activating neutrophil motility, but few classes of antagonists are known. We have explored the structure-activity relationship of a 3-(4-phenyl-1 H-1,2,3-triazol-1-yl)-5-(aryl)benzoic acid antagonist scaffold, assisted by docking and molecular dynamics (MD) simulation at a P2Y14R homology model. A computational pipeline using the High Throughput MD Python environment guided the analogue design. Selection of candidates was based upon ligand-protein shape and complementarity and the persistence of ligand-protein interactions over time. Predictions of a favorable substitution of a 5-phenyl group with thiophene and an insertion of a three-methylene spacer between the 5-aromatic and alkyl amino moieties were largely consistent with empirical results. The substitution of a key carboxylate group on the core phenyl ring with tetrazole or truncation of the 5-aryl group reduced affinity. The most potent antagonists, using a fluorescent assay, were a primary 3-aminopropyl congener 20 (MRS4458) and phenyl p-carboxamide 30 (MRS4478).

Tools and drugs for uracil nucleotide-activated P2Y receptors

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, P2Y₁, P2Y₂, P2Y₄, P2Y₆, P2Y₁₁, P2Y₁₂, P2Y₁₃, and P2Y₁₄, 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: P2Y₂ (UTP, also ATP and dinucleotides), P2Y₄ (UTP), P2Y₆ (UDP), and P2Y₁₄ (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 P2Y₂R agonists include MRS2698 (6-01, highly selective) and PSB-1114 (6-05, increased metabolic stability). A potent and selective P2Y₂R antagonist is AR-C118925 (10-01). For studies of the P2Y₄R, MRS4062 (3-15) may be used as a selective agonist, while PSB-16133 (10-06) is a selective antagonist. Several potent P2Y₆R 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 P2Y₆R antagonist, although its reactivity and low water-solubility are limiting. With MRS2905 (6-08), a potent and metabolically stable P2Y₁₄R agonist is available, while PPTN (10-14) represents a potent and selective P2Y₁₄R antagonist. The radioligand [³H]UDP can be used to label P2Y₁₄Rs. 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.