P2X7 Receptor at the Crossroads of T Cell Fate

Could P2X7 receptor be a potencial target in neonatal sepsis?

The United Nations Inter-Agency Group for Child Mortality Estimation (UNIGME) estimates that every year 2.5 million neonates die in their first month of life, accounting for nearly one-half of deaths in children under 5 years of age. Neonatal sepsis is the third leading cause of neonatal mortality. The worldwide burden of bacterial sepsis is expected to increase in the next decades due to the lack of effective molecular therapies to replace the administration of antibiotics whose efficacy is compromised by the emergence of resistant strains. In addition, prolonged exposure to antibiotics can have negative effects by increasing the risk of infection by other organisms. With the global burden of sepsis increasing and no vaccine nor other therapeutic approaches proved efficient, the World Health Organization (WHO) stresses the need for new therapeutic targets for sepsis treatment and infection prevention (WHO, A73/32). In response to this unresolved clinical issue, the P2X7 receptor (P2X7R), a key component of the inflammatory cascade, has emerged as a potential target for treating inflammatory/infection diseases. Indeed numerous studies have demonstrated the relevance of the purinergic system as a pharmacological target in addressing immune-mediated inflammatory diseases by regulating immunity, inflammation, and organ function. In this review, we analyze key features of sepsis immunopathophysiology focusing in neonatal sepsis and on how the immunomodulatory role of P2X7R could be a potential pharmacological target for reducing the burden of neonatal sepsis.

Extracellular adenosine triphosphate: A new gateway for food allergy mechanism research?

Although various studies have been conducted, the detailed mechanisms of food allergy remain a topic of ongoing debate. Recently, researchers have reported that extracellular adenosine triphosphate (eATP), a member of damage-associated molecular patterns secreted by stressed cells, plays a critical role in the progression of asthma and atopic dermatitis. These studies suggest that dysregulated eATP significantly influences various aspects of disease progression, from bodily sensitization to the emergence of clinical manifestations. Given the shared pathogenic mechanisms among asthma, atopic dermatitis, and food allergies, we hypothesize that eATP may also serve as a crucial regulator in the development of food allergies. To elucidate this hypothesis, we first summarize the evidence and limitations of food allergy theories, then discuss the roles of eATP in allergic diseases. We conclude with speculative insights into the potential influence of eATP on food allergy development, aiming to inspire further investigation into the molecular mechanisms of food allergies.

Tumor microenvironment induced switch to mitochondrial metabolism promotes suppressive functions in immune cells

Understanding the intricacies of the metabolic phenotype in immune cells and its plasticity within the tumor microenvironment is pivotal in understanding the pathology and prognosis of cancer. Unfavorable conditions and cellular stress in the tumor microenvironment (TME) exert a profound impact on cellular functions in immune cells, thereby influencing both tumor progression and immune responses. Elevated AMP:ATP ratio, a consequence of limited glucose levels, activate AMP-activated protein kinase (AMPK) while concurrently repressing the activity of mechanistic target of rapamycin (mTOR) and hypoxia-inducible factor 1-alpha (HIF-1α). The intricate balance between AMPK, mTOR, and HIF-1α activities defines the metabolic phenotype of immune cells in the TME. These Changes in metabolic phenotype are strongly associated with immune cell functions and play a crucial role in creating a milieu conducive to tumor progression. Insufficiency of nutrient and oxygen supply leads to a metabolic shift in immune cells characterized by a decrease in glycolysis and an increase in oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) rates. In most cases, this shift in metabolism is accompanied by a compromise in the effector functions of these immune cells. This metabolic adaptation prompts immune cells to turn down their effector functions, entering a quiescent or immunosuppressive state that may support tumor growth. This article discusses how tumor microenvironment alters the metabolism in immune cells leading to their tolerance and tumor progression, with emphasis on mitochondrial metabolism (OXPHOS and FAO).

Functional role of P2X7 purinergic receptor in cancer and cancer-related pain

Numerous studies have revealed that the ATP-gated ion channel purinergic 2X7 receptor (P2X7R) plays an important role in tumor progression and the pathogenesis of cancer pain. P2X7R requires activation by extracellular ATP to perform its regulatory role functions. During tumor development or cancer-induced pain, ATP is released from tumor cells or other cells in the tumor microenvironment (such as tumor-associated immune cells), which activates P2X7R, opens ion channels on the cell membrane, affects intracellular molecular metabolism, and regulates the activity of tumor cells. Furthermore, peripheral organs and receptors can be damaged during tumor progression, and P2X7R expression in nerve cells (such as microglia) is significantly upregulated, enhancing sensory afferent information, sensitizing the central nervous system, and inducing or exacerbating pain. These findings reveal that the ATP-P2X7R signaling axis plays a key regulatory role in the pathogenesis of tumors and cancer pain and also has a therapeutic role. Accordingly, in this study, we explored the role of P2X7R in tumors and cancer pain, discussed the pharmacological properties of inhibiting P2X7R activity (such as the use of antagonists) or blocking its expression in the treatment of tumor and cancer pain, and provided an important evidence for the treatment of both in the future.

Purinergic ligands induce extracellular acidification and increased ATP turnover in HepG2 cells

Nucleosides and nucleotides at μM concentrations stimulated a 300% increase in acid secretion in HepG2 cells, which was quantitatively accounted for as increased export of lactate generated by glycogenolysis. Agonist selectivity encompassed nucleosides and nucleotides for all 5 natural nucleobases and, along with antagonist profiles, was inconsistent with a role for purinergic receptors in mediating this activity. Agonist catabolism did not contribute significantly to either low selectivity or lactate production. Lactate production was driven by an increase in ATP turnover of as much as 56%. For some agonists, especially adenosine, ATP turnover decreased precipitously at mM concentrations, correlating with known adenosine-stimulated apoptosis. We propose that nucleoside/nucleotide agonists induce a futile energy cycle via a novel mechanism, which results in increased ATP turnover and initiates a continuum of events that for some agonists culminates in apoptosis.

P2X7 receptors: a bibliometric review from 2002 to 2023

For many years, there has been ongoing research on the P2X7 receptor (P2X7R). A comprehensive, systematic, and objective evaluation of the scientific output and status of P2X7R will be instrumental in guiding future research directions. This study aims to present the status and trends of P2X7R research from 2002 to 2023. Publications related to P2X7R were retrieved from the Web of Science Core Collection database. Quantitative analysis and visualization tools were Microsoft Excel, VOSviewer, and CiteSpace software. The analysis content included publication trends, literature co-citation, and keywords. 3282 records were included in total, with the majority of papers published within the last 10 years. Based on literature co-citation and keyword analysis, neuroinflammation, neuropathic pain, gastrointestinal diseases, tumor microenvironment, rheumatoid arthritis, age-related macular degeneration, and P2X7R antagonists were considered to be the hotspots and frontiers of P2X7R research. Researchers will get a more intuitive understanding of the status and trends of P2X7R research from this study.

P2X7 Receptor in Dendritic Cells and Macrophages: Implications in Antigen Presentation and T Lymphocyte Activation

The P2X7 receptor, a member of the P2X purinergic receptor family, is a non-selective ion channel. Over the years, it has been associated with various biological functions, from modulating to regulating inflammation. However, its emerging role in antigen presentation has captured the scientific community's attention. This function is essential for the immune system to identify and respond to external threats, such as pathogens and tumor cells, through T lymphocytes. New studies show that the P2X7 receptor is crucial for controlling how antigens are presented and how T cells are activated. These studies focus on antigen-presenting cells, like dendritic cells and macrophages. This review examines how the P2X7 receptor interferes with effective antigen presentation and activates T cells and discusses the fundamental mechanisms that can affect the immune response. Understanding these P2X7-mediated processes in great detail opens up exciting opportunities to create new immunological therapies.

Ion channel P2X7 receptor in the progression of cancer

P2X7 receptor (P2X7) is a non-selective and ATP-sensitive ligand-gated cation channel. Studies have confirmed that it is expressed in a variety of cells and correlates with their function, frequently in immune cells and tumor cells. We found increased expression of this receptor in many tumor cells, and it has a role in tumor survival and progression. In immune cells, upregulation of the receptor has a double effect on tumor suppression as well as tumor promotion. This review describes the structure of P2X7 and its role in the tumor microenvironment and presents possible mechanisms of P2X7 in tumor invasion and metastasis. Understanding the potential of P2X7 for tumor treatment, we also present several therapeutic agents targeting P2X7 and their mechanisms of action. In conclusion, the study of P2X7 is an important guideline for the use of clinical tumor therapy and may be able to provide a new idea for tumor treatment, but considering the complexity of the biological effects of P2X7, the drugs should be used with caution in clinical practice.

Extracellular ATP (eATP) inhibits the progression of endometriosis and enhances the immune function of macrophages

BACKGROUND

Extracellular adenosine triphosphate (eATP) is an important inflammatory mediator that can boost the antitumour immune response, but its role in endometriosis remains unknown. We hypothesized that eATP could inhibit endometriosis cell function both directly and indirectly through macrophages.

METHODS

Peritoneal and cyst fluid from endometriosis patients and non-endometriosis controls was collected to measure eATP levels. The addition of eATP was performed to explore its effects on endometriotic cell and macrophage functions, including cell proliferation, apoptosis, pyroptosis, mitochondrial membrane potential, phagocytosis, and the production of inflammatory cytokines and reactive oxygen species. A coculture of endometriotic epithelial cells and U937 macrophages was established, followed by P2X7 antagonist and eATP treatment. Endometriosis model eATP-treated rats were used to evaluate in situ cell death and macrophage marker expression.

RESULTS

The pelvic microenvironment of endometriosis patients shows high eATP levels, which could induce endometriotic epithelial cell apoptosis and pyroptosis and significantly inhibit cell growth via the MAPK/JNK/Akt pathway. eATP treatment ameliorated endometriosis-related macrophage dysfunction and promoted macrophage recruitment. eATP treatment in the presence of macrophages exerted a stronger cytotoxic effect on endometriotic epithelial cells by regulating P2X7. eATP treatment effectively induced cell death in an endometriosis rat model and prominently increased the macrophage number without affecting the eutopic endometrium.

CONCLUSION

eATP induces endometriotic epithelial cell death and enhances the immune function of macrophages to inhibit the progression of endometriosis, while eutopic endometrium is not affected. eATP treatment may serve as a nonhormonal therapeutic strategy for endometriosis.

ATP ion channel P2X7 receptor as a regulatory molecule in the progression of colorectal cancer

Large amounts of adenosine triphosphate (ATP), a natural P2X7 receptor activator, are released during colorectal carcinogenesis. P2X7 receptor activation regulates the activity of colorectal cancer (CRC) cells by mediating intracellular signal transduction. Importantly, the opening and activation of membrane pores of P2X7 receptor are different, which can play a dual role in promoting or inhibiting the progression of CRC. These can also depend on P2X7 receptor to regulate the activities of immune cells in the microenvironment, play the functions of immune regulation, immune escape and immune monitoring. While the use of P2X7 receptor antagonists (such as BBG, A438079 and A740003) can play a certain inhibitory pharmacological role on the activity of CRC. Therefore, in this paper, the mechanism and immunomodulatory function of P2X7 receptor involved in the progression of CRC were discussed. Moreover, we discussed the effect of antagonizing the activity of P2X7 receptor on the progression of CRC. So P2X7 receptor may be a new pharmacological molecular target for the treatment of CRC.

P2RX7 gene knockout or antagonism reduces angiotensin II-induced hypertension, vascular injury and immune cell activation

OBJECTIVE

Extracellular ATP is elevated in hypertensive mice and humans and may trigger immune activation through the purinergic receptor P2X7 (P2RX7) causing interleukin-1β production and T-cell activation and memory T-cell development. Furthermore, P2RX7 single nucleotide polymorphisms (SNP) are associated with hypertension. We hypothesized that P2RX7 activation contributes to hypertension and cardiovascular injury by promoting immune activation.

METHODS

Male wild-type and P2rx7-/- mice were infused or not with angiotensin II (AngII) for 14 days. A second group of AngII-infused wild-type mice were co-infused with the P2RX7 antagonist AZ10606120 or vehicle. BP was monitored by telemetry. Cardiac and mesenteric artery function and remodeling were assessed using ultrasound and pressure myography, respectively. T cells were profiled in thoracic aorta/perivascular adipose tissue by flow cytometry. Associations between SNPs within 50 kb of P2RX7 transcription, and BP or hypertension were modeled in 384 653 UK Biobank participants.

RESULTS

P2rx7 inactivation attenuated AngII-induced SBP elevation, and mesenteric artery dysfunction and remodeling. This was associated with decreased perivascular infiltration of activated and effector memory T-cell subsets. Surprisingly, P2rx7 knockout exaggerated AngII-induced cardiac dysfunction and remodeling. Treatment with a P2RX7 antagonist reduced BP elevation, preserved mesenteric artery function and reduced activated and effector memory T cell perivascular infiltration without adversely affecting cardiac function and remodeling in AngII-infused mice. Three P2RX7 SNPs were associated with increased odds of DBP elevation.

CONCLUSION

P2RX7 may represent a target for attenuating BP elevation and associated vascular damage by decreasing immune activation.

Tumour immune escape via P2X7 receptor signalling

While P2X7 receptor expression on tumour cells has been characterized as a promotor of cancer growth and metastasis, its expression by the host immune system is central for orchestration of both innate and adaptive immune responses against cancer. The role of P2X7R in anti-tumour immunity is complex and preclinical studies have described opposing roles of the P2X7R in regulating immune responses against tumours. Therefore, few P2X7R modulators have reached clinical testing in cancer patients. Here, we review the prognostic value of P2X7R in cancer, how P2X7R have been targeted to date in tumour models, and we discuss four aspects of how tumours skew immune responses to promote immune escape via the P2X7R; non-pore functional P2X7Rs, mono-ADP-ribosyltransferases, ectonucleotidases, and immunoregulatory cells. Lastly, we discuss alternative approaches to offset tumour immune escape via P2X7R to enhance immunotherapeutic strategies in cancer patients.

The Role of P2X7 Purinoceptors in the Pathogenesis and Treatment of Muscular Dystrophies

Muscular dystrophies are inherited neuromuscular diseases, resulting in progressive disability and often affecting life expectancy. The most severe, common types are Duchenne muscular dystrophy (DMD) and Limb-girdle sarcoglycanopathy, which cause advancing muscle weakness and wasting. These diseases share a common pathomechanism where, due to the loss of the anchoring dystrophin (DMD, dystrophinopathy) or due to mutations in sarcoglycan-encoding genes (LGMDR3 to LGMDR6), the α-sarcoglycan ecto-ATPase activity is lost. This disturbs important purinergic signaling: An acute muscle injury causes the release of large quantities of ATP, which acts as a damage-associated molecular pattern (DAMP). DAMPs trigger inflammation that clears dead tissues and initiates regeneration that eventually restores normal muscle function. However, in DMD and LGMD, the loss of ecto-ATPase activity, that normally curtails this extracellular ATP (eATP)-evoked stimulation, causes exceedingly high eATP levels. Thus, in dystrophic muscles, the acute inflammation becomes chronic and damaging. The very high eATP over-activates P2X7 purinoceptors, not only maintaining the inflammation but also tuning the potentially compensatory P2X7 up-regulation in dystrophic muscle cells into a cell-damaging mechanism exacerbating the pathology. Thus, the P2X7 receptor in dystrophic muscles is a specific therapeutic target. Accordingly, the P2X7 blockade alleviated dystrophic damage in mouse models of dystrophinopathy and sarcoglycanopathy. Therefore, the existing P2X7 blockers should be considered for the treatment of these highly debilitating diseases. This review aims to present the current understanding of the eATP-P2X7 purinoceptor axis in the pathogenesis and treatment of muscular dystrophies.

Animal Models for the Investigation of P2X7 Receptors

The P2X7 receptor is a trimeric ligand-gated cation channel activated by extracellular adenosine 5'-triphosphate. The study of animals has greatly advanced the investigation of P2X7 and helped to establish the numerous physiological and pathophysiological roles of this receptor in human health and disease. Following a short overview of the P2X7 distribution, roles and functional properties, this article discusses how animal models have contributed to the generation of P2X7-specific antibodies and nanobodies (including biologics), recombinant receptors and radioligands to study P2X7 as well as to the pharmacokinetic testing of P2X7 antagonists. This article then outlines how mouse and rat models have been used to study P2X7. These sections include discussions on preclinical disease models, polymorphic P2X7 variants, P2X7 knockout mice (including bone marrow chimeras and conditional knockouts), P2X7 reporter mice, humanized P2X7 mice and P2X7 knockout rats. Finally, this article reviews the limited number of studies involving guinea pigs, rabbits, monkeys (rhesus macaques), dogs, cats, zebrafish, and other fish species (seabream, ayu sweetfish, rainbow trout and Japanese flounder) to study P2X7.

Activated P2X receptors can up-regulate the expressions of inflammation-related genes via NF-κB pathway in spotted sea bass (Lateolabrax maculatus)

P2X receptors, including seven subtypes, i.e., P2X1-7, are the ligand-gated ion channels activated by the extracellular ATP playing the critical roles in inflammation and immune response. Even though the immune functions of P2X receptors have been characterized extensively in mammals, their functions in fish remain largely unknown. In this study, four P2X receptor homologues were characterized in spotted sea bass (Lateolabrax maculatus), which were named LmP2X2, LmP2X4, LmP2X5, and LmP2X7. Their tissue distributions and expression patterns were then investigated by real-time quantitative PCR (qPCR). Furthermore, their functions in regulating the expressions of inflammation-associated genes and possible signaling pathway were examined by qPCR and luciferase assay. The results showed that they share similar topological structures, conserved genomic organization, and gene synteny with their counterparts in other species previously investigated. And the four P2X receptors were expressed constitutively in the tested tissues. In addition, the expression of each of the four receptor genes was significantly induced by stimulation of Edwardsiella tarda and/or pathogen-associated molecular patterns (PAMPs) in vivo. Also, in primary head kidney leukocytes of spotted sea bass, LmP2X2 and LmP2X5 were induced by using PAMPs and/or ATP. Notably, the expressions of CCL2, IL-8, and TNF-α recognized as the pro-inflammatory cytokines, and of the four apoptosis-related genes, i.e., caspase3, caspase6, caspase7, and P53, were differentially upregulated in the HEK 293T cells with over-expressed LmP2X2 and/or LmP2X7 following ATP stimulation. Also, the over-expression of LmP2X4 can upregulate the expressions of IL-8, caspase6, caspase7, and P53, and LmP2X5 upregulates of IL-8, TNF-α, caspase7, and P53. Then in the present study it was demonstrated that the activation of any one of the four receptors significantly upregulated the activity of NF-κB promoter, suggesting that the activated LmP2Xs may regulate the expressions of pro-inflammatory cytokines via the NF-κB pathway. Taken together, the four P2X receptors were identified firstly from fish species in Perciformes, and they participate in innate immune response of spotted sea bass possibly by regulating the expressions of the inflammation-related genes. Our study provides the new evidences for the P2X receptors' involvement in fish immunity.

The P2X7 purinoceptor in pathogenesis and treatment of dystrophino- and sarcoglycanopathies

Dystrophinopathy and sarcoglycanopathies are incurable diseases caused by mutations in the genes encoding dystrophin or members of the dystrophin associated protein complex (DAPC). Restoration of the missing dystrophin or sarcoglycans via genetic approaches is complicated by the downsides of personalised medicines and immune responses against re-expressed proteins. Thus, the targeting of disease mechanisms downstream from the mutant protein has a strong translational potential. Acute muscle damage causes release of large quantities of ATP, which activates P2X7 purinoceptors, resulting in inflammation that clears dead tissues and triggers regeneration. However, in dystrophic muscles, loss of α-sarcoglycan ecto-ATPase activity further elevates extracellular ATP (eATP) levels, exacerbating the pathology. Moreover, seemingly compensatory P2X7 upregulation in dystrophic muscle cells, combined with high eATP leads to further damage. Accordingly, P2X7 blockade alleviated dystrophic damage in mouse models of both dystrophinopathy and sarcoglycanopathy. Existing P2X7 blockers could be re-purposed for the treatment of these highly debilitating diseases.

Damage-induced NAD release activates intestinal CD4+ and CD8+ T cell via P2X7R signaling

BACKGROUND

Postoperative ileus (POI) is characterized by the activation of inflammation triggered by tissue damage. Damage-associated molecular patterns (DAMPs) reportedly induce local inflammation after injury. However, the impact of DAMPs on intestinal resident lymphocytes during POI remains poorly elucidated.

METHODS

POI in mice was induced via intestinal manipulation (IM). The concentration of nicotinamide adenine dinucleotide (NAD) was detected after IM. The gastrointestinal motility of the mice was assessed after IM or NAD injection. Cytokine production and calcium influx in T cells were investigated after NAD stimulation using flow cytometry.

RESULTS

The concentration of extracellular NAD significantly increased after IM administration, and NAD directly impaired gastrointestinal motility. Intraperitoneal injection of NAD promoted the expression of TNF-α in intestinal CD8+ and CD4+ T cells, but only IFN-γ production by CD8+ T cells was significantly promoted by NAD injection. Granzyme B production in CD8+ and CD4+ T cells decreased after administration. Concordantly, the same results were observed in NAD stimulation of intestinal CD3+ T cells in vitro. Blocking the P2X7R-related membrane enzyme ART2.2 significantly diminished the pro-inflammatory effect of NAD.

CONCLUSION

IM includes the release of NAD derived from damaged tissues, consequently promoting pro-inflammatory cytokine production in intestinal CD4+ and CD8+ T lymphocytes. NAD-induced intestinal T cells activation may be associated with POI progression in the mouse.

Research progress on the P2X7 receptor in liver injury and hepatocellular carcinoma

Purinergic ligand-gated ion channel 7 receptor (P2X7 receptor) is an adenosine triphosphate (ATP)-gated ion channel that is widely distributed on the surfaces of immune cells and tissues such as those in the liver, kidney, lung, intestine, and nervous system. Hepatocellular carcinoma (HCC) is one of the most common malignancies with increasing incidence and mortality. Although many treatments for liver cancer have been studied, the prognosis for liver cancer is still very poor. Therefore, new liver cancer treatments are urgently needed. P2X7 receptor activation can secrete proinflammatory factors through the P2X7 receptor-NLRP3 signaling pathway, thereby affecting the progression of liver injury. The P2X7 receptor may be a target for growth inhibition of HCC cells and may affect the invasion and migration of HCC cells through the PI3K/AKT and AMPK signaling pathways. In recent years, P2X7 receptor antagonists or inhibitors have attracted widespread attention as therapeutic targets for hepatocellular carcinoma and liver injury. Therefore, this review covers the basic concepts of the P2X7 receptor and role of the P2X7 receptor in liver cancer and liver injury, providing new potential therapeutic targets for hepatocellular carcinoma and liver injury.

The human P2X7 receptor alters microglial morphology and cytokine secretion following immunomodulation

Introduction: In recent years, purinergic signaling via the P2X7 receptor (P2X7R) on microglia has repeatedly been implicated in depression genesis. However, it remains unclear which role the human P2X7R (hP2X7R) plays in regulating both microglia morphology and cytokine secretion upon different environmental and immune stimuli, respectively. Methods: For this purpose, we used primary microglial cultures derived from a humanized microglia-specific conditional P2X7R knockout mouse line to emulate different gene-environment interactions between microglial hP2X7R and molecular proxies of psychosocial and pathogen-derived immune stimuli. Microglial cultures were subjected to treatments with the agonists 2'(3')-O-(4-benzoylbenzoyl)-ATP (BzATP) and lipopolysaccharides (LPS) combined with specific P2X7R antagonists (JNJ-47965567, A-804598). Results: Morphotyping revealed overall high baseline activation due to the in vitro conditions. Both BzATP and LPS + BzATP treatment increased round/ameboid microglia and decreased polarized and ramified morphotypes. This effect was stronger in hP2X7R-proficient (CTRL) compared to knockout (KO) microglia. Aptly, we found antagonism with JNJ-4796556 and A-804598 to reduce round/ameboid microglia and increase complex morphologies only in CTRL but not KO microglia. Single cell shape descriptor analysis confirmed the morphotyping results. Compared to KO microglia, hP2X7R-targeted stimulation in CTRLs led to a more pronounced increase in microglial roundness and circularity along with an overall higher decrease in aspect ratio and shape complexity. JNJ-4796556 and A-804598, on the other hand, led to opposite dynamics. In KO microglia, similar trends were observed, yet the magnitude of responses was much smaller. Parallel assessment of 10 cytokines demonstrated the proinflammatory properties of hP2X7R. Following LPS + BzATP stimulation, IL-1β, IL-6, and TNFα levels were found to be higher and IL-4 levels lower in CTRL than in KO cultures. Vice versa, hP2X7R antagonists reduced proinflammatory cytokine levels and increased IL-4 secretion. Discussion: Taken together, our results help disentangle the complex function of microglial hP2X7R downstream of various immune stimuli. In addition, this is the first study in a humanized, microglia-specific in vitro model identifying a so far unknown potential link between microglial hP2X7R function and IL-27 levels.

Two Single Nucleotide Polymorphisms in the Purinergic Receptor P2X7 Gene Are Associated with Disease Severity in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic autoimmune inflammatory disease of the central nervous system (CNS) that leads to progressive physical disability. Recent evidence has suggested that P2X7 receptor (P2X7R)-mediated purinergic signalling pathways play a role in MS-associated neuroinflammation, possibly contributing to disease pathogenesis. To evaluate possible associations between P2X7R polymorphisms and MS disease severity, we performed an association study of five non-synonymous SNPs coding variants of the P2X7R gene: rs1718119 Ala348Thr, rs2230911 Thr357Ser, rs2230912 Gln460Arg, rs3751143 Glu496Ala, and rs28360457 Arg307Gln, modulating P2X7R expression in 128 MS patients (relapsing remitting MS, RRMS: n = 94; secondary progressive, SPMS: n = 34). All patients were genotyped, and multiple sclerosis severity score (MSSS) was evaluated in every case; 189 healthy subjects were enrolled as well as controls. Results showed that P2X7R rs1718119(A) 348Thr and rs22390912(G) 464Arg, two SNPs of minor allele frequency (MAF) known to confer gain of function to the P2X7R protein, were associated with significantly higher MSSS in RRMS patients alone (SMRR (p < 0.001, p = 0.01, respectively)). Interestingly, two whole haplotypes resulted in having significant association with MSSS in these same patients. Thus: (1) the P2X7R-4 “ACGAG” haplotype, characterized by the co-presence of the rs1718119-rs2230912 AG MAF alleles, was associated with higher MSSS (Beta: 1.11 p = 0.04), and (2) the P2X7R-1 “GCAAG” complementary haplotype, which contains the rs1718119 and rs2230912 GA wild-type alleles, was more frequently carried by patients with lower MSSS and less severe disease (Beta: −1.54 p < 0.001). Although being preliminary and needing confirmation in an ampler cohort, these results suggest that 348Thr and 464Arg variants have a role as modulators of disease severity in RRMS patients.

P2X7 receptor as the regulator of T-cell function in intestinal barrier disruption

The intestinal mucosa is a highly compartmentalized structure that forms a direct barrier between the host intestine and the environment, and its dysfunction could result in a serious disease. As T cells, which are important components of the mucosal immune system, interact with gut microbiota and maintain intestinal homeostasis, they may be involved in the process of intestinal barrier dysfunction. P2X7 receptor (P2X7R), a member of the P2X receptors family, mediates the effects of extracellular adenosine triphosphate and is expressed by most innate or adaptive immune cells, including T cells. Current evidence has demonstrated that P2X7R is involved in inflammation and mediates the survival and differentiation of T lymphocytes, indicating its potential role in the regulation of T cell function. In this review, we summarize the available research about the regulatory role and mechanism of P2X7R on the intestinal mucosa-derived T cells in the setting of intestinal barrier dysfunction.

Contribution of P2X purinergic receptor in cerebral ischemia injury

The development of cerebral ischemia involves brain damage and abnormal changes in brain function, which can cause neurosensory and motor dysfunction, and bring serious consequences to patients. P2X purinergic receptors are expressed in nerve cells and immune cells, and are mainly expressed in microglia. The P2X4 and P2X7 receptors in the P2X purinergic receptors play a significant role in regulating the activity of microglia. Moreover, ATP-P2X purine information transmission is involved in the progression of neurological diseases, including the release of pro-inflammatory factors, driving factors and cytokines after cerebral ischemia injury, inducing inflammation, and aggravating cerebral ischemia injury. P2X receptors activation can mediate the information exchange between microglia and neurons, induce neuronal apoptosis, and aggravate neurological dysfunction after cerebral ischemia. However, inhibiting the activation of P2X receptors, reducing their expression, inhibiting the activation of microglia, and has the effect of protecting nerve function. In this paper, we discussed the relationship between P2X receptors and nervous system function and the role of microglia activation inducing cerebral ischemia injury. Additionally, we explored the potential role of P2X receptors in the progression of cerebral ischemic injury and their potential pharmacological targets for the treatment of cerebral ischemic injury.

P2 Receptors: Novel Disease Markers and Metabolic Checkpoints in Immune Cells

Extracellular ATP (eATP) and P2 receptors are novel emerging regulators of T-lymphocyte responses. Cellular ATP is released via multiple pathways and accumulates at sites of tissue damage and inflammation. P2 receptor expression and function are affected by numerous single nucleotide polymorphisms (SNPs) associated with diverse disease conditions. Stimulation by released nucleotides (purinergic signalling) modulates several T-lymphocyte functions, among which energy metabolism. Energy metabolism, whether oxidative or glycolytic, in turn deeply affects T-cell activation, differentiation and effector responses. Specific P2R subtypes, among which the P2X7 receptor (P2X7R), are either up- or down-regulated during T-cell activation and differentiation; thus, they can be considered indexes of activation/quiescence, reporters of T-cell metabolic status and, in principle, markers of immune-mediated disease conditions.

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.

Extracellular ATP Limits Homeostatic T Cell Migration Within Lymph Nodes

Whereas adenosine 5'-triphosphate (ATP) is the major energy source in cells, extracellular ATP (eATP) released from activated/damaged cells is widely thought to represent a potent damage-associated molecular pattern that promotes inflammatory responses. Here, we provide suggestive evidence that eATP is constitutively produced in the uninflamed lymph node (LN) paracortex by naïve T cells responding to C-C chemokine receptor type 7 (CCR7) ligand chemokines. Consistently, eATP was markedly reduced in naïve T cell-depleted LNs, including those of nude mice, CCR7-deficient mice, and mice subjected to the interruption of the afferent lymphatics in local LNs. Stimulation with a CCR7 ligand chemokine, CCL19, induced ATP release from LN cells, which inhibited CCR7-dependent lymphocyte migration in vitro by a mechanism dependent on the purinoreceptor P2X7 (P2X7R), and P2X7R inhibition enhanced T cell retention in LNs in vivo. These results collectively indicate that paracortical eATP is produced by naïve T cells in response to constitutively expressed chemokines, and that eATP negatively regulates CCR7-mediated lymphocyte migration within LNs via a specific subtype of ATP receptor, demonstrating its fine-tuning role in homeostatic cell migration within LNs.

Schistosomes Impede ATP-Induced T Cell Apoptosis In Vitro: The Role of Ectoenzyme SmNPP5

Schistosomes (blood flukes) can survive in the bloodstream of their hosts for many years. We hypothesize that proteins on their host-interactive surface impinge on host biochemistry to help ensure their long-term survival. Here, we focus on a surface ectoenzyme of Schistosoma mansoni, designated SmNPP5. This ~53 kDa glycoprotein is a nucleotide pyrophosphatase/phosphodiesterase that has been previously shown to: (1) cleave adenosine diphosphate (ADP) and block platelet aggregation; and (2) cleave nicotinamide adenine dinucleotide (NAD) and block NAD-induced T cell apoptosis in vitro. T cell apoptosis can additionally be driven by extracellular adenosine triphosphate (ATP). In this work, we show that adult S. mansoni parasites can inhibit this process. Further, we demonstrate that recombinant SmNPP5 alone can both cleave ATP and impede ATP-induced T cell killing. As immunomodulatory regulatory T cells (Tregs) are especially prone to the induction of these apoptotic pathways, we hypothesize that the schistosome cleavage of both NAD and ATP promotes Treg survival and this helps to create a less immunologically hostile environment for the worms in vivo.

P2X7 receptor is essential for cross-dressing of bone marrow-derived dendritic cells

T cell activation requires the processing and presentation of antigenic peptides in the context of a major histocompatibility complex (MHC complex). Cross-dressing is a non-conventional antigen presentation mechanism, involving the transfer of preformed peptide/MHC complexes from whole cells, such as apoptotic cells (ACs) to the cell membrane of professional antigen-presenting cells (APCs), such as dendritic cells (DCs). This is an essential mechanism for the induction of immune response against viral antigens, tumors, and graft rejection, which until now has not been clarified. Here we show for first time that the P2X7 receptor (P2X7R) is crucial to induce cross-dressing between ACs and Bone-Marrow DCs (BMDCs). In controlled ex vivo assays, we found that the P2X7R in both ACs and BMDCs is required to induce membrane and fully functional peptide/MHC complex transfer to BMDCs. These findings show that acquisition of ACs-derived preformed antigen/MHC-I complexes by BMDCs requires P2X7R expression.

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Cross-dressing of antigens to Dendritic Cells (DCs) is dependent of P2X7 receptor

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The P2X7 receptor must be present in both Dendritic Cells and antigen source

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The transfer of antigen/MHC-I complexes to DCs is functional and activates T CD8 cells

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The P2X7 receptor allows Cross-Dressing possibly through a membrane fusion process

The role of P2X7 receptor in infection and metabolism: Based on inflammation and immunity

The P2X7 receptor (P2X7R) is a ligand-gated receptor belonging to the P2 receptor family. It is distributed in various tissues of the human body and is involved in regulating the physiological functions of tissues and cells to affect the occurrence and development of diseases. Unlike all other P2 receptors, the P2X7 receptor is mainly expressed in immune cells and can be activated not only by extracellular nucleotides but also by non-nucleotide substances which act as positive allosteric modulators. In this review, we comprehensively describe the role of the P2X7 receptor in infection and metabolism based on its role as an important regulator of inflammation and immunity, and briefly introduce the structure and general function of the P2X7 receptor. These provide a clear knowledge framework for the study of the P2X7 receptor in human health. Targeting the P2X7 receptor may be an effective method for the treatment of inflammatory and immune diseases. And its role in microbial infection and metabolism may be the main direction for in-depth research on the P2X7 receptor in the future.

Role of P2X7 Receptors in Immune Responses During Neurodegeneration

P2X7 receptors are ion-gated channels activated by ATP. Under pathological conditions, the extensive release of ATP induces sustained P2X7 receptor activation, culminating in induction of proinflammatory pathways with inflammasome assembly and cytokine release. These inflammatory conditions, whether occurring peripherally or in the central nervous system (CNS), increase blood-brain-barrier (BBB) permeability. Besides its well-known involvement in neurodegeneration and neuroinflammation, the P2X7 receptor may induce BBB disruption and chemotaxis of peripheral immune cells to the CNS, resulting in brain parenchyma infiltration. For instance, despite common effects on cytokine release, P2X7 receptor signaling is also associated with metalloproteinase secretion and activation, as well as migration and differentiation of T lymphocytes, monocytes and dendritic cells. Here we highlight that peripheral immune cells mediate the pathogenesis of Multiple Sclerosis and Parkinson's and Alzheimer's disease, mainly through T lymphocyte, neutrophil and monocyte infiltration. We propose that P2X7 receptor activation contributes to neurodegenerative disease progression beyond its known effects on the CNS. This review discusses how P2X7 receptor activation mediates responses of peripheral immune cells within the inflamed CNS, as occurring in the aforementioned diseases.

Role of the purinergic signaling network in lung ischemia-reperfusion injury

PURPOSE OF REVIEW

Primary graft dysfunction (PGD) is the leading cause of early mortality following lung transplantation and is typically caused by lung ischemia-reperfusion injury (IRI). Current management of PGD is largely supportive and there are no approved therapies to prevent lung IRI after transplantation. The purinergic signaling network plays an important role in this sterile inflammatory process, and pharmacologic manipulation of said network is a promising therapeutic strategy. This review will summarize recent findings in this area.

RECENT FINDINGS

In the past 18 months, our understanding of lung IRI has improved, and it is becoming clear that the purinergic signaling network plays a vital role. Recent works have identified critical components of the purinergic signaling network (Pannexin-1 channels, ectonucleotidases, purinergic P1 and P2 receptors) involved in inflammation in a number of pathologic states including lung IRI. In addition, a functionally-related calcium channel, the transient receptor potential vanilloid type 4 (TRPV4) channel, has recently been linked to purinergic signaling and has also been shown to mediate lung IRI.

SUMMARY

Agents targeting components of the purinergic signaling network are promising potential therapeutics to limit inflammation associated with lung IRI and thus decrease the risk of developing PGD.

Adenosine triphosphate, polymyxin B and B16 cell-derived immunization induce anticancer response

Aim: Whole dead tumor cells can be used as antigen source and the induction of protective immune response could be enhanced by damage-associated molecular patterns. Materials & methods: We generated whole dead tumor cells called B16-immunogenic cell bodies (ICBs) from B16 melanoma cells by nutrient starvation and evaluated the in vivo antitumor effect of B16-ICBs plus ATP and polymyxin B (PMB). Results: The subcutaneous immunization with B16-ICBs + PMB + ATP a 50% of tumor-free animals and induced a significant delay in tumor growth in a prophylactic approach. These results correlated with maturation of bone marrow-derived dendritic cells and activation of T CD8⁺ lymphocytes in vitro. Conclusion: Altogether, ICB + ATP + PMB is efficient in inducing the antitumor efficacy of the whole dead tumor cells vaccine.