P2Y12 receptor-mediated cyclooxygenase 2 (COX-2) expression enhances tumor cell progression in a mouse model of lymphoma.

The pro-inflammatory enzyme cyclooxygenase 2 (COX-2) has been known to impart metastatic property to cancer cells. However, blocking of COX-2 with nonsteroidal anti-inflammatory drugs or COX-2-specific inhibitors has failed in clinical trials due to adverse effects associated with their prolonged use. We have previously shown that extracellular ATP (eATP), a major component of the tumor microenvironment, enhances COX-2 expression several-fold, both in macrophages and in various cancer cells, by acting on purinergic (P2) receptors. In this study, we show that blocking of P2 receptors significantly reduced tumor growth in a mouse model of lymphoma. Tumors were induced in mice through subcutaneous injection of syngeneic EL4 lymphoma cells. Various P2 receptor antagonists were injected within the tumors after they were palpable. The broad-spectrum P2 receptor antagonist, suramin, P2X7 receptor-specific antagonist, oATP, P2Y6 receptor-specific antagonist, MRS 2578, and P2Y12 receptor-specific antagonist, AR-C 69931, all showed significant arrest in tumor growth. Both suramin and AR-C 69931-treated tumors showed strong reduction in COX-2 expression and modulation of various metastatic markers. Disaggregated cells from AR-C 69931-treated tumors, when injected intravenously in naïve mice, did not exhibit metastasis in various tissues which was observed in mice injected with cells from saline-treated tumors. Our results show that blocking of P2 receptors is a therapeutic alternative to inhibit COX-2 expression, and thereby, arrest tumor progression and metastasis.

The anti-inflammatory and tolerogenic potential of small spleen peptides.

Maintaining peripheral immune tolerance and preventing harmful autoimmune reactions is a fundamental task of the immune system. However, these essential functions are significantly compromised during autoimmune disorders, creating a major challenge in treating these conditions. In this context, we provide an overview of research on small spleen polypeptides (SSPs) that naturally regulate peripheral immune tolerance. Alongside outlining the observed effects of SSPs, we summarize here the findings on the cellular and molecular mechanisms that underlie their regulatory impact. Specifically, SSPs have demonstrated remarkable effectiveness in halting the progression of developing or established autoimmune disorders like psoriasis or arthritis in animal models. They primarily target dendritic cells (DCs), swiftly prompting the production of extracellular ATP, which is then degraded and sensed by adenosine receptors. This process triggers the mTOR signaling cascade, similar to powerful immune triggers, but instead of a rapid and intense reaction, it leads to a moderate yet significant activation of the mTOR signaling cascade. This induces a tolerogenic state in dendritic cells, ultimately leading to the generation of Foxp3+ immunosuppressor Treg cells. In addition, SSPs may indirectly attenuate the autoimmune response by reducing extracellular ATP synthesis in non-immune cells, such as endothelial cells, when exposed to elevated levels of proinflammatory cytokines. SSPs thus have the potential to contribute to the restoration of peripheral immune tolerance and may offer valuable therapeutic benefits in treating autoimmune diseases.

Overview of the role of purinergic signaling and insights into its role in cancer therapy.

Innovation of cancer therapy has received a dramatic acceleration over the last fifteen years thanks to the introduction of the novel immune checkpoint inhibitors (ICI). On the other hand, the conspicuous scientific knowledge accumulated in purinergic signaling since the early seventies is finally being transferred to the clinic. Several Phase I/II clinical trials are currently underway to investigate the effect of drugs interfering with purinergic signaling as stand-alone or combination therapy in cancer. This is supporting the novel concept of "purinergic immune checkpoint" (PIC) in cancer therapy. In the present review we will address a) the basic pharmacology and cell biology of the purinergic system; b) principles of its pathophysiology in human diseases; c) implications for cell death, cell proliferation and cancer; d) novel molecular tools to investigate nucleotide homeostasis in the extracellular environment; e) recent developments in the pharmacology of P1, P2 receptors and related ecto-enzymes; f) P1 and P2 ligands as novel diagnostic tools; g) current issues in PIC-based anti-cancer therapy. This review will provide an appraisal of the current status of purinergic signaling in cancer and will help identify future avenues of development.

[Corrigendum] P2Y2 receptor promotes the migration and invasion of breast cancer cells via EMT­related genes Snail and E­cadherin.

Subsequently to the publication of the above paper, an interested reader drew to the authors' attention that there appeared to be two instances of overlapping data panels comparing between the cell migration and invasion assay data shown in Figs. 4 and 6 on p. 143 and 145, respectively, such that data which were intended to represent the results from differently performed experiments had apparently been derived from the same original sources. In addition, the authors themselves realized that incorrect western blotting data for Snail protein in Fig. 10A on p. 147 had been included in the figure.  The authors were able to re­examine their original data files, and realized that the affected data panels in these figures had inadvertently been incorporated into them incorrectly. The revised versions of Figs. 4, 6, and 10, featuring the correct data for the 'NC / Control' panels in Fig. 4B and C and the 'siRNA2 / ATP 12 h' panels in Fig. 4A and B, a replacement data panel for the 'siRNA1 / Control' experiment in Fig. 6, and the correct western blotting data for Snail protein in Fig. 10A (together with a revised histogram for the MCF7 cell line relating to Fig. 10A) are shown on the next three pages. The authors wish to emphasize that the errors made in compiling these figures did not affect the overall conclusions reported in the paper, and they are grateful to the Editor of Oncology Reports for allowing them the opportunity to publish this corrigendum. All the authors agree to the publication of this corrigendum, and also apologize to the readership for any inconvenience caused. [Oncology Reports 39: 138­150, 2018; DOI: 10.3892/or.2017.6081].

Mentha piperita leaf extract suppresses the release of ATP from epidermal keratinocytes and reduces dermal thinning as well as wrinkle formation.

OBJECTIVES: To achieve a more beautiful and younger appearance, reducing wrinkles is a key concern. The process of wrinkle formation is complex and the development of truly effective cosmetic ingredients to reduce wrinkles remains a challenge. Recent studies have revealed a close relationship between wrinkles and skin thinning, suggesting that preventing skin thinning could also prevent wrinkle formation. In this study, we examined the role of extracellular adenosine triphosphate (eATP) in the progression of thinning, as eATP reportedly increases skin ageing factors, such as senescence-associated secreted phenotype (SASP) factors in epidermal cells. We determined the effects of Mentha piperita leaf extract on suppressing eATP to reduce thinning and wrinkles. METHODS: Adenosine triphosphate (ATP) levels were measured in normal human epidermal keratinocytes (NHEK) in the presence of M. piperita leaf extract. Dryness, high pH, and UVB radiation were used as extrinsic ageing factors. Intrinsic skin ageing was evaluated by comparing cells from adults (AD-NHEK) and newborns (NB-NHEK). A placebo-controlled in vivo study was carried out with a formulation containing 1% M. piperita leaf extract. RESULTS: The eATP levels were significantly higher in AD-NHEK compared with that in NB-NHEK cells. M. piperita leaf extract significantly decreased eATP levels in adult cells. Extrinsic ageing factors increased eATP levels in NHEK, whereas M. piperita leaf extract significantly suppressed eATP under all conditions. The active components of M. piperita leaf extract, luteolin glucuronide and rosmarinic acid, also decreased eATP. Moreover, compared with placebo lotion, M. piperita leaf extract-formulated lotion markedly increased dermal thickness and reduced wrinkles associated with crow's feet and the neck area. CONCLUSION: We demonstrated for the first time that M. piperita leaf extract containing rosmarinic acid and luteolin-7-O-glucuronide has the potential to reduce eATP release from epidermal keratinocytes. An increase in eATP was observed not only during inflammation but also during natural ageing. Furthermore, the in vivo experiment revealing that 1% M. piperita leaf extract-containing lotion improved dermal thinning and wrinkles across multiple areas is attributed to the amelioration of dermal thinning. Thus, our data suggest the possibility of a novel cosmetic approach for reducing skin ageing by reducing eATP-mediated dermal thinning.

OBJECTIFS: Pour obtenir une apparence plus belle et plus jeune, réduire les rides est une préoccupation clé. Le processus de formation des rides est complexe et le développement d'ingrédients cosmétiques réellement efficaces pour réduire les rides reste un défi. Des études récentes ont révélé une relation étroite entre les rides et l'amincissement de la peau, suggérant que la prévention de l'amincissement de la peau pourrait également prévenir la formation de rides. Dans cette étude, nous avons examiné le rôle de l'adénosine triphosphate extracellulaire (eATP) dans la progression de l'amincissement, car l'eATP augmente apparemment les facteurs de vieillissement de la peau, tels que les facteurs du phénotype sécrétoire associé à la sénescence (SASP) dans les cellules épidermiques. Nous avons déterminé les effets de l'extrait de feuille de Mentha piperita sur la suppression de l'eATP pour réduire l'amincissement et les rides. MÉTHODES: Les niveaux d'adénosine triphosphate (ATP) ont été mesurés dans les kératinocytes épidermiques humains normaux (NHEK) en présence d'extrait de feuille de M. piperita. La sécheresse, le pH élevé et les radiations UVB ont été utilisés comme facteurs de vieillissement extrinsèque. Le vieillissement intrinsèque de la peau a été évalué en comparant les cellules des adultes (AD­NHEK) et des nouveau­nés (NB­NHEK). Une étude in vivo contrôlée par placebo a été réalisée avec une formulation contenant 1% d'extrait de feuille de M. piperita. RÉSULTATS: Les niveaux d'eATP étaient significativement plus élevés dans les AD­NHEK comparés à ceux des cellules NB­NHEK. L'extrait de feuille de M. piperita a significativement diminué les niveaux d'eATP dans les cellules adultes. Les facteurs de vieillissement extrinsèque ont augmenté les niveaux d'eATP dans les NHEK, tandis que l'extrait de feuille de M. piperita a significativement supprimé l'eATP dans toutes les conditions. Les composants actifs de l'extrait de feuille de M. piperita, la lutéoline glucuronide et l'acide rosmarinique, ont également diminué l'eATP. De plus, comparée à la lotion placebo, la lotion formulée avec de l'extrait de feuille de M. piperita a considérablement augmenté l'épaisseur dermique et réduit les rides associées aux pattes d'oie et à la région du cou. CONCLUSION: Nous avons démontré pour la première fois que l'extrait de feuille de M. piperita contenant de l'acide rosmarinique et de la lutéoline­7­O­glucuronide a le potentiel de réduire la libération d'eATP des kératinocytes épidermiques. Une augmentation de l'eATP a été observée non seulement pendant l'inflammation mais aussi pendant le vieillissement naturel. En outre, l'expérience in vivo révélant que la lotion contenant 1% d'extrait de feuille de M. piperita a amélioré l'amincissement dermique et les rides sur plusieurs zones est attribuée à l'amélioration de l'amincissement dermique. Ainsi, nos données suggèrent la possibilité d'une nouvelle approche cosmétique pour réduire le vieillissement de la peau en réduisant l'amincissement dermique médié par l'eATP.

Metabolic crosstalk: Extracellular ATP and the tumor microenvironment in cancer progression and therapy.

Adenosine 5'-triphosphate (ATP) is a vital element in energy information. It plays a critical role in transmitting signals inside the body, which is necessary for controlling the life activities of all cells, including tumor cells [1]. Its significance extends from intracellular signaling pathways to tumor regression. Purinergic signaling, a form of extracellular paracrine signaling, relies on purine nucleotides. Extracellular ectonucleotidases convert these purine nucleotides to their respective di and mono-phosphate nucleoside forms, contributing significantly to immune biology, cancer biology, and inflammation studies. ATP functions as a mighty damage-linked molecular pattern when released outside the cell, accumulating in inflammatory areas. In the tumor microenvironment (TME), purinergic receptors such as ATP-gated ion channels P2X1-5 and G protein-coupled receptors (GPCR) (P2Y) interact with ATP and other nucleotides, influencing diverse immune cell activities. CD39 and CD73-mediated extracellular ATP degradation contributes to immunosuppression by diminishing ATP-dependent activation and generating adenosine (ADO), potentially hindering antitumor immunity and promoting tumor development. Unraveling the complexities of extracellular ATP (e-ATP) and ADO effects on the TME poses challenges in identifying optimal treatment targets, yet ongoing investigations aim to devise strategies combating e-ATP/ADO-induced immunosuppression, ultimately enhancing anti-tumor immunity. This review explores e-ATP metabolism, its purinergic signaling, and therapeutic strategies targeting associated receptors and enzymes.

The activation of Piezo1 channel promotes invasion and migration via the release of extracellular ATP in cervical cancer.

BACKGROUND: The mechanosensitive ion channel Piezo1 has emerged as a potential prognostic and therapeutic target in different types of cancers. The aim of this study was to determine the expression levels and underlying mechanisms of Piezo1 in the invasion and migration processes in cervical cancer. METHODS: Initially, we employed qRT-PCR, western blot, and immunohistochemical staining techniques to assess the disparity in Piezo1 expression in cervical cancer tissues and cells. Subsequently, we conducted wound healing, transwell assays and phalloidin staining to observe the effects of stable Piezo1 silencing and Piezo1 selective agonist Yoda1 on the invasion and migration capabilities. The release of extracellular ATP was assessed using the enhanced ATP assay kit. Furthermore, we conducted rescue experiments to investigate whether the activation of Piezo1 facilitates cervical cancer invasion and migration through extracellular ATP. Finally, we constructed xenograft tumor models to determine weather the Piezo1 selective agonist Yoda1 influenced the tumor growth in vivo. RESULTS: In our study, we found that Piezo1 expression was elevated in both cervical cancer tissues and cells, with the highest levels observed in patients with lymph node metastasis. Knocking down Piezo1 resulted in a significant reduction in the invasion and migration capabilities of cervical cancer cells, whereas the use of the Piezo1 selective agonist Yoda1 enhanced these capabilities. Moreover, the activation of Piezo1 channels was found to regulate the release of extracellular ATP. Mechanistically, the activation of Piezo1 might facilitate cervical cancer invasion, migration, and pseudopodium formation through the release of extracellular ATP. And Piezo1 was an important molecule for the tumor growth of cervical cancer in vivo. CONCLUSION: Our findings revealed that Piezo1 facilitated the invasion and migration of cervical cancer by releasing extracellular ATP, which might hold potential as a valuable target for prognostic and therapeutic interventions in cervical cancer.

FERONIA orchestrates P2K1-driven purinergic signaling in plant roots.

Extracellular ATP (eATP) orchestrates vital processes in plants, akin to its role in animals. P2K1 is a crucial receptor mediating eATP effects. Immunoprecipitation tandem mass spectrometry data highlighted FERONIA's significant interaction with P2K1, driving us to explore its role in eATP signaling. Here, we investigated putative P2K1-interactor, FERONIA, which is a versatile receptor kinase pivotal in growth and stress responses. We employed a FERONIA loss-of-function mutant, fer-4, to dissect its effects on eATP signaling. Interestingly, fer-4 showed distinct calcium responses compared to wild type, while eATP-responsive genes were constitutively upregulated in fer-4. Additionally, fer-4 displayed insensitivity to eATP-regulated root growth and reduced cell wall accumulation. Together, these results uncover a role for FERONIA in regulating eATP signaling. Overall, our study deepens our understanding of eATP signaling, revealing the intricate interplay between P2K1 and FERONIA impacting the interface between growth and defense.

Small Spleen Peptides (SSPs) Shape Dendritic Cell Differentiation through Modulation of Extracellular ATP Synthesis Profile.

Restoring peripheral immune tolerance is crucial for addressing autoimmune diseases. An ancient mechanism in maintaining the balance between inflammation and tolerance is the ratio of extracellular ATP (exATP) and adenosine. Our previous research demonstrated the effectiveness of small spleen peptides (SSPs) in inhibiting psoriatic arthritis progression, even in the presence of the pro-inflammatory cytokine TNFα, by transforming dendritic cells (DCs) into tolerogenic cells and fostering regulatory Foxp3+ Treg cells. Here, we identified thymosins as the primary constituents of SSPs, but recombinant thymosin peptides were less efficient in inhibiting arthritis than SSPs. Since Tß4 is an ecto-ATPase-binding protein, we hypothesized that SSPs regulate exATP profiles. Real-time investigation of exATP levels in DCs revealed that tolerogenic stimulation led to robust de novo exATP synthesis followed by significant degradation, while immunogenic stimulation resulted in a less pronounced increase in exATP and less effective degradation. These contrasting exATP profiles were crucial in determining whether DCs entered an inflammatory or tolerogenic state, highlighting the significance of SSPs as natural regulators of peripheral immunological tolerance, with potential therapeutic benefits for autoimmune diseases. Finally, we demonstrated that the tolerogenic phenotype of SSPs is mainly influenced by adenosine receptors, and in vivo administration of SSPs inhibits psoriatic skin inflammation.

Extracellular ATP Is a Homeostatic Messenger That Mediates Cell-Cell Communication in Physiological Processes and Psychiatric Diseases.

Neuronal activity is the basis of information encoding and processing in the brain. During neuronal activation, intracellular ATP (adenosine triphosphate) is generated to meet the high-energy demands. Simultaneously, ATP is secreted, increasing the extracellular ATP concentration and acting as a homeostatic messenger that mediates cell-cell communication to prevent aberrant hyperexcitability of the nervous system. In addition to the confined release and fast synaptic signaling of classic neurotransmitters within synaptic clefts, ATP can be released by all brain cells, diffuses widely, and targets different types of purinergic receptors on neurons and glial cells, making it possible to orchestrate brain neuronal activity and participate in various physiological processes, such as sleep and wakefulness, learning and memory, and feeding. Dysregulation of extracellular ATP leads to a destabilizing effect on the neural network, as found in the etiopathology of many psychiatric diseases, including depression, anxiety, schizophrenia, and autism spectrum disorder. In this review, we summarize advances in the understanding of the mechanisms by which extracellular ATP serves as an intercellular signaling molecule to regulate neural activity, with a focus on how it maintains the homeostasis of neural networks. In particular, we also focus on neural activity issues that result from dysregulation of extracellular ATP and propose that aberrant levels of extracellular ATP may play a role in the etiopathology of some psychiatric diseases, highlighting the potential therapeutic targets of ATP signaling in the treatment of these psychiatric diseases. Finally, we suggest potential avenues to further elucidate the role of extracellular ATP in intercellular communication and psychiatric diseases.

Murine and Human-Purified very Small Embryonic-like Stem Cells (VSELs) Express Purinergic Receptors and Migrate to Extracellular ATP Gradient.

Purinergic signaling is an ancient primordial signaling system regulating tissue development and specification of various types of stem cells. Thus, functional purinergic receptors are present in several types of cells in the body, including multiple populations of stem cells. However, one stem cell type that has not been evaluated for expression of purinergic receptors is very small embryonic stem cells (VSELs) isolated from postnatal tissues. Herein, we report that human umbilical cord blood (UCB) and murine bone marrow (BM) purified VSELs express mRNA for P1 and P2 purinergic receptors and CD39 and CD73 ectonucleotidases converting extracellular ATP (eATP) into its signaling metabolite extracellular adenosine (eAdo), that antagonizes eATP effects. More importantly, we demonstrate that human and murine VSELs respond by chemotaxis to eATP, and eAdo inhibits this migration. These responses to eATP are mediated by activation of Nlrp3 inflammasome, and exposure of VSELs to its specific inhibitor MCC950 abolished the chemotactic response to ATP. We conclude that purinergic signaling plays an essential, underappreciated role in the biology of these cells and their potential role in response to tissue/organ injuries.

Unveiling orphan receptor-like kinases in plants: novel client discovery using high-confidence library predictions in the Kinase-Client (KiC) assay.

Plants are remarkable in their ability to adapt to changing environments, with receptor-like kinases (RLKs) playing a pivotal role in perceiving and transmitting environmental cues into cellular responses. Despite extensive research on RLKs from the plant kingdom, the function and activity of many kinases, i.e., their substrates or "clients", remain uncharted. To validate a novel client prediction workflow and learn more about an important RLK, this study focuses on P2K1 (DORN1), which acts as a receptor for extracellular ATP (eATP), playing a crucial role in plant stress resistance and immunity. We designed a Kinase-Client (KiC) assay library of 225 synthetic peptides, incorporating previously identified P2K phosphorylated peptides and novel predictions from a deep-learning phosphorylation site prediction model (MUsite) and a trained hidden Markov model (HMM) based tool, HMMER. Screening the library against purified P2K1 cytosolic domain (CD), we identified 46 putative substrates, including 34 novel clients, 27 of which may be novel peptides, not previously identified experimentally. Gene Ontology (GO) analysis among phosphopeptide candidates revealed proteins associated with important biological processes in metabolism, structure development, and response to stress, as well as molecular functions of kinase activity, catalytic activity, and transferase activity. We offer selection criteria for efficient further in vivo experiments to confirm these discoveries. This approach not only expands our knowledge of P2K1's substrates and functions but also highlights effective prediction algorithms for identifying additional potential substrates. Overall, the results support use of the KiC assay as a valuable tool in unraveling the complexities of plant phosphorylation and provide a foundation for predicting the phosphorylation landscape of plant species based on peptide library results.

Imaging of extracellular and intracellular ATP in pancreatic beta cells reveals correlation between glucose metabolism and purinergic signalling.

Adenosine triphosphate (ATP) is a universal energy molecule and yet cells release it and extracellular ATP is an important signalling molecule between cells. Monitoring of ATP levels outside of cells is important for our understanding of physiological and pathophysiological processes in cells/tissues. Here, we focus on pancreatic beta cells (INS-1E) and test the hypothesis that there is an association between intra- and extracellular ATP levels which depends on glucose provision. We imaged real-time changes in extracellular ATP in pancreatic beta cells using two sensors tethered to extracellular aspects of the plasma membrane (eATeam3.10, iATPSnFR1.0). Increase in glucose induced fast micromolar ATP release to the cell surface, depending on glucose concentrations. Chronic pre-treatment with glucose increased the basal ATP signal. In addition, we co-expressed intracellular ATP sensors (ATeam1.30, PercevalHR) in the same cultures and showed that glucose induced fast increases in extracellular and intracellular ATP. Glucose and extracellular ATP stimulated glucose transport monitored by the glucose sensor (FLII12Pglu-700uDelta6). In conclusion, we propose that in beta cells there is a dynamic relation between intra- and extracellular ATP that depends on glucose transport and metabolism and these processes may be tuned by purinergic signalling. Future development of ATP sensors for imaging may aid development of novel approaches to target extracellular ATP in, for example, type 2 diabetes mellitus therapy.

CPK28 is a modulator of purinergic signaling in plant growth and defense.

Extracellular ATP (eATP) is a key signaling molecule that plays a pivotal role in plant growth and defense responses. The receptor P2K1 is responsible for perceiving eATP and initiating its signaling cascade. However, the signal transduction mechanisms downstream of P2K1 activation remain incompletely understood. We conducted a comprehensive analysis of the P2K1 interactome using co-immunoprecipitation-coupled tandem mass spectrometry, leading to the identification of 121 candidate proteins interacting with P2K1. In silico analysis narrowed down the candidates to 47 proteins, including Ca2+-binding proteins, ion transport-related proteins, and receptor kinases. To investigate their involvement in eATP signaling, we employed a screening strategy based on changes in gene expression in response to eATP in mutants of the identified interactors. This screening revealed several Ca2+-dependent protein kinases (CPKs) that significantly affected the expression of eATP-responsive genes, suggesting their potential roles in eATP signaling. Notably, CPK28 and CPK6 showed physical interactions with P2K1 both in yeast and plant systems. Calcium influx and gene expression studies demonstrated that CPK28 perturbed eATP-induced Ca2+ mobilization and some early transcriptional responses. Overexpression of CPK28 resulted in an antagonistic physiological response to P2K1-mediated eATP signaling during both plant growth and defense responses to the necrotrophic pathogen Botrytis cinerea. Our findings highlight CPK28, among other CPKs, as a modulator of P2K1-mediated eATP signaling, providing valuable insights into the coordination of eATP signaling in plant growth and immunity.

Extracellular ATP- and adenosine-mediated purinergic signaling modulates inducible nitric oxide synthase (iNOS) gene expression, enzyme activity and nitric oxide production in common carp (Cyprinus carpio) head kidney macrophages.

Inducible nitric oxide (NO) synthase (iNOS) is a key immune mediator for production of inflammatory mediator NO from l-arginine. Tight regulation of iNOS expression and enzyme activity is critical for proper NO productions under inflammation and infection conditions. However, the regulatory mechanism for iNOS expression and enzyme activity in fish remains largely unknown. Here, we show that extracellular ATP treatment significantly up-regulates iNOS gene expression and enzyme activity, and consequently leads to enhanced NO production in Cyprinus carpio head kidney macrophages (HKMs). We further show that the extracellular ATP-induced iNOS enzyme activity and NO production can be attenuated by pharmacological inhibition of the ATP-gated P2X4 and P2X7 receptors with their respective specific antagonists, but enhanced by overexpression of P2X4 and P2X7 receptors in grass carp ovary cells. In contrast, adenosine administration significantly reduces iNOS gene expression, enzyme activity and NO production in carp HKMs, and these inhibitory effects can be reversed by pharmacological inhibition of adenosine receptors with the antagonist XAC. Furthermore, LPS- and poly(I:C)-induced iNOS gene expression, enzyme activity, and NO production are significantly attenuated by blockade of P2X4 and P2X7 receptors with their respective specific antagonists in carp HKMs, while overexpression of P2X and P2X7 receptors results in enhanced iNOS gene expression, enzyme activity and NO production in LPS- and poly(I:C)-treated grass carp ovary cells. Taken together, we firstly report an opposite role of extracellular ATP/adenosine-mediated purinergic signaling in modulating iNOS-NO system activity in fish.

Aerobic glycolysis of bronchial epithelial cells rewires Mycoplasma pneumoniae pneumonia and promotes bacterial elimination.

The immune response to Mycoplasma pneumoniae infection plays a key role in clinical symptoms. Previous investigations focused on the pro-inflammatory effects of leukocytes and the pivotal role of epithelial cell metabolic status in finely modulating the inflammatory response have been neglected. Herein, we examined how glycolysis in airway epithelial cells is affected by M. pneumoniae infection in an in vitro model. Additionally, we investigated the contribution of ATP to pulmonary inflammation. Metabolic analysis revealed a marked metabolic shift in bronchial epithelial cells during M. pneumoniae infection, characterized by increased glucose uptake, enhanced aerobic glycolysis, and augmented ATP synthesis. Notably, these metabolic alterations are orchestrated by adaptor proteins, MyD88 and TRAM. The resulting synthesized ATP is released into the extracellular milieu via vesicular exocytosis and pannexin protein channels, leading to a substantial increase in extracellular ATP levels. The conditioned medium supernatant from M. pneumoniae-infected epithelial cells enhances the secretion of both interleukin (IL)-1ß and IL-18 by peripheral blood mononuclear cells, partially mediated by the P2X7 purine receptor (P2X7R). In vivo experiments confirm that addition of a conditioned medium exacerbates pulmonary inflammation, which can be attenuated by pre-treatment with a P2X7R inhibitor. Collectively, these findings highlight the significance of airway epithelial aerobic glycolysis in enhancing the pulmonary inflammatory response and aiding pathogen clearance.

Extracellular adenosine triphosphate regulates inflammatory responses of periodontal ligament cells.

BACKGROUND: Various stimuli, that is, mechanical stresses or inflammation, induce the release of adenosine triphosphate (ATP) by human periodontal ligament cells (HPDLCs). Extracellular adenosine triphosphate (eATP) affects HPDLCs' functions such as immunosuppressive action and inflammatory responses. Lipopolysaccharide (LPS) is the key factor involved in periodontal inflammation. However, the possible correlation and detailed mechanism of inflammation-mediated eATP by LPS and inflammatory cascade formation in HPDLCs is unclarified. This study aims to examine the role of eATP on the HPDLCs' responses concerning inflammatory actions after LPS treatment. METHODS: HPDLCs were stimulated with Porphyromonas gingivalis LPS and polyinosinic:polycytidylic acid (poly I:C). The amount of ATP release was measured at different time points using a bioluminescence assay. HPDLCs were treated with eATP. The expression of pro-inflammatory and anti-inflammatory genes was determined. Specific P2X purinoreceptor 7 (P2X7) inhibitors (brilliant blue G [BBG] and KN62), a specific P2Y purinoreceptor 1 (P2Y1) inhibitors (MRS2179), calcium chelator (EGTA), protein kinase C (PKC) inhibitors, nuclear factor kappa-light-chain-enhancer of activated B cells (NF𝜅B) activation inhibitors, and cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) inhibitors (H89 dihydrochloride) and activators (forskolin) were used to dissect the mechanism of eATP-induced HPDLCs' inflammatory responses. RESULTS: LPS and poly I:C induced ATP release. A low concentration of eATP (50 µM) increased pro-inflammatory genes (COX2, IL1B, IL6, IL8, IL12, and TNFA), while a high concentration (500 µM) enhanced anti-inflammatory genes (IL4 and IL10). BBG, KN62, and NF𝜅B activation inhibitors impeded eATP-induced pro-inflammatory genes. MRS2179 and H89 markedly suppressed eATP-induced anti-inflammatory genes. Forskolin induced IL4 and IL10. CONCLUSION: HPDLCs respond to LPS by releasing ATP. eATP has dose-dependent dual functions on HPDLCs' inflammatory responses via different pathways. As regulation of inflammation is important in regeneration, eATP may help to limit inflammation and trigger periodontal regeneration.

Analysis of Extracellular ATP Distribution in the Intervertebral Disc.

Progressive loss of proteoglycans (PGs) is the major biochemical change during intervertebral disc (IVD) degeneration. Adenosine triphosphate (ATP) as the primary energy source is not only critical for cell survival but also serves as a building block in PG synthesis. Extracellular ATP can mediate a variety of physiological functions and was shown to promote extracellular matrix (ECM) production in the IVD. Therefore, the objective of this study was to develop a 3D finite element model to predict extracellular ATP distribution in the IVD and evaluate the impact of degeneration on extracellular ATP distribution. A novel 3D finite element model of the IVD was developed by incorporating experimental measurements of ATP metabolism and ATP-PG binding kinetics into the mechano-electrochemical mixture theory. The new model was validated by experimental data of porcine IVD, and then used to analyze the extracellular distribution of ATP in human IVDs. Extracellular ATP was shown to bind specifically with PGs in IVD ECM. It was found that annulus fibrosus cells hydrolyze ATP faster than that of nucleus pulposus (NP) cells whereas NP cells exhibited a higher ATP release. The distribution of extracellular ATP in a porcine model was consistent with experimental data in our previous study. The predictions from a human IVD model showed a high accumulation of extracellular ATP in the NP region, whereas the extracellular ATP level was reduced with tissue degeneration. This study provides an understanding of extracellular ATP metabolism and its potential biological influences on the IVD via purinergic signaling.

The Plasma Membrane Purinoreceptor P2K1/DORN1 Is Essential in Stomatal Closure Evoked by Extracellular Diadenosine Tetraphosphate (Ap4A) in Arabidopsis thaliana.

Dinucleoside polyphosphates (NpnNs) are considered novel signalling molecules involved in the induction of plant defence mechanisms. However, NpnN signal recognition and transduction are still enigmatic. Therefore, the aim of our research was the identification of the NpnN receptor and signal transduction pathways evoked by these nucleotides. Earlier, we proved that purine and pyrimidine NpnNs differentially affect the phenylpropanoid pathway in Vitis vinifera suspension-cultured cells. Here, we report, for the first time, that both diadenosine tetraphosphate (Ap4A) and dicytidine tetraphosphate (Cp4C)-induced stomatal closure in Arabidopsis thaliana. Moreover, we showed that plasma membrane purinoreceptor P2K1/DORN1 (does not respond to nucleotide 1) is essential for Ap4A-induced stomata movements but not for Cp4C. Wild-type Col-0 and the dorn1-3 A. thaliana knockout mutant were used. Examination of the leaf epidermis dorn1-3 mutant provided evidence that P2K1/DORN1 is a part of the signal transduction pathway in stomatal closure evoked by extracellular Ap4A but not by Cp4C. Reactive oxygen species (ROS) are involved in signal transduction caused by Ap4A and Cp4C, leading to stomatal closure. Ap4A induced and Cp4C suppressed the transcriptional response in wild-type plants. Moreover, in dorn1-3 leaves, the effect of Ap4A on gene expression was impaired. The interaction between P2K1/DORN1 and Ap4A leads to changes in the transcription of signalling hubs in signal transduction pathways.