Hemorrhagic shock (HS) leads to systemic hypoperfusion, impaired tissue oxygenation, and multi-organ dysfunction, including central nervous system (CNS) injury. Guanosine and inosine, purine nucleosides with neuroprotective and anti-inflammatory properties, have demonstrated beneficial effects in models of neurotoxicity, ischemia, and septic shock. This study evaluated the acute effects of guanosine and inosine in fluid resuscitation, focusing on brain energy metabolism, neuroinflammatory mechanisms, and hemodynamic responses in a porcine model of HS. Thirty pigs (25-30 kg) underwent controlled hemorrhage to achieve a target mean arterial pressure (MAP) of 40 - 45 mmHg, maintained for 60 min. Animals were randomized into three resuscitation groups: Lactated Ringer's solution (LR), LR + guanosine (1 mmol/L), and LR + inosine (1 mmol/L), administered over 15 - 20 min. Hemodynamic, metabolic, and neuronal parameters were monitored for 440 min post-HS, with serial blood and cerebrospinal fluid (CSF) sampling to assess glutamate, lactate, glucose, neuron-specific enolase (NSE), and inflammatory cytokines. HS induced metabolic acidosis, increased CSF glutamate levels, and elevated proinflammatory cytokines (IL-1β, TNF-α, IFN-γ, IL-8). Guanosine and inosine reduced glutamate levels more rapidly than LR alone and attenuated IL-1β and TNF-α elevations. Inosine resuscitation improved MAP, systemic vascular resistance index (SVRI), and end-diastolic volume index (EDVI), suggesting enhanced hemodynamic stabilization. Guanosine and inosine modulated neuroinflammatory and metabolic responses in HS, reducing excitotoxicity and inflammatory cytokine release. Inosine also demonstrated hemodynamic benefits. These findings support further investigation into their therapeutic potential in shock resuscitation.

Adenosine is a key modulator in the pathophysiology of acute kidney injury (AKI), particularly through its influence on inflammatory pathways and renal hemodynamics. This nucleoside exerts its effects via four G protein-coupled receptors-A1, A2A, A2B, and A3-each displaying distinct roles during renal injury. The A1 receptor primarily protects renal tissue under ischemic conditions by reducing metabolic demand, while the A2A receptor promotes anti-inflammatory and vasodilatory effects, improving renal perfusion and attenuating leukocyte infiltration. The A2B receptor, upregulated under hypoxic or injury conditions, is involved in anti-inflammatory actions and vascular integrity, especially in renal tubular and endothelial cells. Conversely, activation of the A3 receptor is generally linked to adverse outcomes, including increased apoptosis and greater tissue damage. Therapeutic strategies targeting adenosine receptors are being actively explored: selective A1 and A2A agonists show potential for promoting renal recovery, while A3 antagonists helped counteract the harmful effects of A3 activation. The review also discusses advances from recent studies (2022-2024), including insights on COVID-19-associated AKI and the nuanced roles of A1 and A3 receptors in different pathological contexts. Additionally, the therapeutic promise of inhibiting adenosine-degrading enzymes, such as ADA and adenosine kinase (ADK), is highlighted. Novel mechanistic insights and recent literature are integrated, providing a comprehensive overview that expands upon previous reviews. Although adenosine receptor modulation holds significant promise as a therapeutic strategy for AKI, further clinical research is necessary to validate efficacy and safety in human populations.

Prostate cancer (PCa) preferentially metastasizes to bone, which remains incurable and contributes significantly to mortality and morbidity. The P2X4 receptor (P2X4R) is a receptor for ATP that is highly expressed in many cancer types including PCa and is positively associated with tumorigenesis. To understand the role of P2X4R in PCa biology, particularly in PCa bone metastasis, P2X4R (P2RX4) was knocked out in human PCa cell line PC3 cells using the CRISPR/Cas9 system. Cell proliferation, apoptosis, migration, and invasion were examined using CyQUANT, Cell Meter Caspase 3/7, scratch and transwell assays. Results showed that depleting P2X4R significantly reduced cell proliferation and invasion and increased apoptosis compared to PC3 wildtype (WT) controls in vitro. To test their metastatic potential in vivo, PC3 WT and knock-out (KO) cells were intracardiacally injected into male BALB/c immunocompromised mice. Twenty-five days post-injection, there were no detectable tumours and associated bone destruction in the tibias of mice injected with KO cells, whereas tibias of over 50% mice injected with WT cells were occupied by tumour cells, with significant bone destruction observed ex vivo using micro-CT. Furthermore, RNA-seq and bioinformatic analysis of P2X4R KO cells demonstrated links between P2X4R and PCa cell adhesion, and other key signalling such as Wnt signalling. These findings suggest that P2X4R is a potential therapeutic target for PCa metastasis, particularly bone metastasis.

Endometriosis is a chronic gynecological condition characterized by endometrial tissue outside the uterine cavity. Recent research has focused on the relationship between the purinergic system and endometriosis. As a purinergic system component, extracellular adenosine triphosphate (ATP) has been involved as a crucial mediator of chronic pain associated with the disease, as well as P2X3 receptors, which play a key role in sensitization of nerve fibers and generation of nociceptive, neuropathic, and inflammatory pain. In addition, ectonucleotidases such as CD39 and CD73, which regulate ATP hydrolysis, have an altered expression in endometriotic lesions, contributing to extracellular ATP accumulation, intensifying inflammation and pain. Together, immune cells and their product are increased in endometriotic foci and promote the emergence of new lesions through their contribution to retrograde menstruation. Some studies have observed significant changes in mitochondrial respiration, notably decreased oxygen consumption in the affected endometrium. These various cellular processes that are mediated by ATP and adenosine in the uterine cavity and exert effects on immune defense will be herein reviewed in detail to investigate possible inhibitors, their activity, and potential exploration of the purinergic pathway as a therapeutic alternative.

The signaling mechanisms of nucleotides and nucleosides have been extensively studied over the past decades in various conditions affecting distinct organs and tissues. It is well-established that purinergic receptors are expressed in healthy tissues, with expression levels often increasing under pathological conditions. These receptors play crucial roles in numerous physiological and pathological processes, including inflammation, tissue repair, and cellular signaling. However, the purinergic context in the esophagus and its associated pathologies remains poorly understood, representing a significant gap in current knowledge. In this review, we compiled and analyzed the available data on the involvement of P2 purinergic receptors in esophageal diseases, such as gastroesophageal reflux disease and esophageal carcinoma. Specifically, we discuss the pharmacological modulation, functional characterization, and expression patterns of these receptors in various esophageal cell lines and immune tissue samples, under both healthy and pathological conditions. Understanding the mechanisms of action and signaling pathways involving P2 purinergic receptors in the esophagus can offer valuable insights into their biological roles and emphasize their potential as therapeutic targets for future clinical applications.

Periodontitis is a highly prevalent immunoinflammatory disease that compromises the supporting tissues of the teeth, especially the periodontal ligament and alveolar bone. During disease progression, inflammatory responses lead to the release of ATP, which interacts with purinergic receptors such as P2X7R, potentially influencing bone remodeling. Although P2X7R has been studied in bone cells, its specific role in periodontitis remains poorly characterized. This study aimed to evaluate the effects of P2X7R modulation on osteoblastic activity and experimental bone loss. In vitro, P2X7R expression was confirmed in OFCOL II osteoblastic cells. Receptor activation using BzATP significantly reduced cell viability, altered cell morphology, and decreased alkaline phosphatase (ALP) activity (p < 0.05). In vivo, periodontitis was induced in Wistar rats via ligature. Animals were allocated into four groups: (1) Naïve; (2) Periodontitis (saline-treated); (3) BzATP-treated (P2X7R agonist); and (4) BBG-treated (P2X7R antagonist). BzATP aggravated periodontal damage, with increased inflammation, loss of osteoblasts, and disorganization of periodontal ligament fibers. In contrast, BBG improved tissue architecture, reduced inflammatory infiltrate, and increased osteoblast numbers and ALP activity, possibly via the Wnt signaling pathway. These results suggest that P2X7R activation contributes to inflammation-driven bone loss, impairing osteoblast viability and function. Therefore, P2X7R inhibition may serve as a promising pharmacological strategy to preserve bone and periodontal integrity in the context of periodontitis.

Breast cancer (BC) is a multifactorial disease characterized by cell cycle disorder and immune evasion. Studies reveal that the purinergic system (PS) is a mediator of the immune system and actively participates in the inflammatory process in cancer. Also, there is growing debate about the role of oxidative stress (OS) markers and interleukins as predictors of BC progression and invasion. Thus, PS and OS markers, in addition to the expression of interleukins and quantification of extracellular ATP, were evaluated in 39 BC patients, before the beginning of surgical or pharmacological treatment, and in 35 control participants, matched by sex and age. The results show reduced ATP and ADP hydrolysis in platelets, apart from increased extracellular ATP in the BC group. Increased AMP hydrolysis was observed in BC patients' peripheral blood mononuclear cells (PBMCs). BC patients presented elevated oxidative parameters (MDA) and reduced antioxidant parameters (SOD and ascorbic acid), and reduction in interleukins TNF, IL-4, and IL-2. In PBMC from the BC group, the expression of P2X7 gene was significantly higher in relation to the expression of CD39 gene. Also, the expression of CD39 was 1.71 fold higher in tumor samples compared to PBMC from the BC group, and it was 0.11 fold lower in PBMC from the BC group compared to the controls. We conclude that ectoenzymes that hydrolyze ATP and ADP, mainly CD39, present reduced activity in the BC group, promoting an increase in extracellular ATP and culminating in a pro-inflammatory environment, favoring cancer progression. The increase in active oxidants and the reduction in antioxidants contributed to the progression of BC in patients. Finally, TNF and IL-4 demonstrated to be promising prognostic markers in BC patients.

Silicosis, a chronic lung disease, results from prolonged inhalation of silica dust (SiO) in occupational environments, and its pathogenesis remains incompletely elucidated. Studies have shown that alveolar macrophages (AMs) play a pivotal role in its development. These AMs phagocytose the inhaled SiO, which leads to morphological, structural, and functional abnormalities that result in lung fibrosis. During this process, adenosine triphosphate (ATP) not only provides energy for the physiological and pathological activities but also acts as a key intracellular and extracellular signaling molecule and regulates cytokine synthesis and secretion. This complex process has not been systematically summarized. In this study, first, the current data on ATP metabolism in the development of SiO-induced pulmonary fibrosis are introduced. ATP metabolism disorder, caused by impaired production, utilization, or distribution of ATP, disrupts macrophage energy homeostasis. Then, how ATP metabolism disorder affects macrophage morphology and function and the inflammatory and fibrotic processes of the lungs by activating the P2X7 receptor-mediated ATP signaling pathway are discussed. Finally, current therapeutic strategies targeting ATP metabolism disorder and ATP signaling pathways in silicosis are summarized. In conclusion, SiO-induced ATP metabolism disorder indirectly accelerates the progression of silicosis fibrosis.

The P2X7 receptor is a trimeric ion channel purinergic receptor. It plays a crucial part in the pathophysiology of cancers and a variety of inflammatory diseases and is widely expressed in different cell types. Leukemia represents a type of malignant clonal disorder that impacts the hematopoietic stem cells. Chemotherapy is one of the main treatment methods for leukemia, but there are also many side effects. In recent years, targeted therapy is a new treatment method. Research has shown that the progression and occurrence of leukemia is significantly related to the P2X7 receptor. The P2X7 receptor is also involved in the migration and invasion of leukemia cells. Furthermore, the polymorphism of the P2X7 receptor gene also takes on a significant function in the occurrence, development and clinical course of leukemia patients. The P2X7 receptor inhibitors have been found to work better in combination with existing therapeutics. Therefore, the P2X7 receptor may serve as a potential therapeutic target.

Purinergic neurotransmission, a dynamic signaling system using adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine (ADO), uridine diphosphate (UDP), and others, plays a crucial role in brain function. Purinergic signaling is involved in regulating synaptic communication to influence sleep and neuroprotection; malfunction of purinergic signaling contributes to various neurological disorders like pain, epilepsy, and depression. Effective detection methods are crucial for a comprehensive understanding of the multifaceted roles of purinergic signaling in the brain. This review sheds light on advancements in fluorescent indicators, a powerful toolkit for visualizing purinergic activities in living animals. We explore the diverse applications of these indicators in studying purinergic transmission both in health and in diseases. Despite their current strengths, we emphasize the need for continuous development of fluorescent indicators to achieve an even more comprehensive, specific, and quantitative detection of purinergic signaling.

We have previously reported that adenine at high doses interferes with the vasopressin signaling pathway, causes massive diuresis and volume depletion, and ultimately leads to renal failure. In the present study, we examined the effects of adenine on renal salt and water handling in a time course and dose-response study in rats housed in metabolic cages and fed control or adenine-containing diet at 1500, 2000, 2500 mg/kg and euthanized after 1, 3, and 7 weeks. Adenine at 2000 and 2500 mg/kg caused early and significant polyuria, polydipsia, and decreased urine osmolality in a dose-dependent manner without significantly affecting food intake, blood volume, blood electrolyte levels, or acid-base composition. The impaired water balance resulted from the downregulation of apical water channel AQP2 in the outer and inner medulla but not in the cortex. Adenine did not alter electrolytes (Na, K, Cl) excretion at these doses for up to 3 weeks. However, a slight but significant increase in salt excretion was observed in adenine-fed rats for 7 weeks, which correlates with a significant downregulation of NKCC2, mostly in rats fed 2500 mg/kg adenine. Adenine-fed rats exhibited a substantial resistance to vasopressin in response to water deprivation or vasopressin treatment. Lastly, 2500 mg/kg adenine prevented the development of hyponatremia in a rat experimental model of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). In conclusion, adenine acts as an aquaretic agent in the kidney at lower doses and during a short feeding period. It can be used as a vasopressin antagonist in conditions associated with hyponatremia.

In a recent article published in Neuron, Li et al. (Neuron 112(22):3734-3749.e5, 2024) accomplished a major scientific advance by reporting that ATP-sensitive P2X3 receptor-channels (P2X3Rs) in the paraventricular hypothalamus (PVH) specifically regulate visceral pain without affecting somatic pain. On the other hand, vasoactive intestinal polypeptide-sensing receptors (VIPR2) selectively process somatic pain without altering visceral pain. Function-dependent laser capture microdissection sequencing (fLCM-Seq) and immunohistochemistry demonstrated that P2X3Rs and VIPR2 have different transcriptional profiles and belong to the colorectal distension (CRD) and von Frey filament (VFF)-stimulated subgroups of PVH neurons, respectively. An anterograde tracing strategy, in which green fluorescent protein (GFP) was selectively expressed in CRD-labeled or VFF-labeled PVH neurons, showed that PVH neuronal projections terminated exclusively at the ventral part of the lateral septal nucleus (LSV) while the PVH neuronal projections terminated at the caudal part of the zona incerta (ZIC). The PVH circuit selectively responded to visceral pain while remaining unresponsive to somatic pain. By contrast, the PVH circuit selectively responded to somatic pain, while it did not react to visceral pain. Knockdown of P2X3R expression in PVH neurons enhanced the visceral pain threshold without affecting somatic nociception, and the reverse findings were true for the knockdown of the VIPR2 expressing PVH neurons. All these results provide possible new strategies based on central-targeted therapies for the future treatment of visceral and somatic pain, respectively.

Electroacupuncture (EA), as a combination of traditional acupuncture and modern electrotherapy, and has analgesic effects on various acute and chronic pain. It has been proved to ameliorate chronic visceral pain, but its specific role in rectal visceral pain remains underexplored. A capsaicin (CAP)-induced visceral pain rat model was established, and behavioral pain responses were observed and recorded. Measurement of mechanical pain threshold was performed using electronic Von Frey system. Rectal tissues, and the activity of microglia cells were detected by Hematoxylin/eosin staining and immunofluorescence, respectively. Contents of interleukin (IL)-6, IL-1β and tumor necrosis factor-α (TNF-α) were determined by enzyme-linked immunosorbent assay. Western blot was performed to determine the expressions of P2X4 receptor (P2X4R), p38 mitogen-activated protein kinase (p38), phosphorylated p38 (p-p38), transient receptor potential vanilloid-1 (TRPV1) and ionized calcium binding adapter molecule 1 (Iba-1). Transfection efficiency of TRPV1 overexpression plasmids was examined by quantitative real-time polymerase chain reaction. EA abrogated CAP-induced upregulation of behavioral pain responses and mechanical threshold, damage on rectal tissue, activation of microglia, stimulation of inflammatory response and promotion of P2X4R-p38-TRPV1 pathway expressions in rats, while P2X4R activation reversed the effect of EA. P2X4R antagonist weakened CAP-induced upregulation of P2X4R-p38-TRPV1 pathway expressions, microglia activation as well as increase of IL-1β in HMO6 cells, which was reversed by TRPV1 overexpression. Collectively, EA improves CAP-induced rectal visceral pain via inhibiting TRPV1 expression by blocking the P2X4R-activated p38 pathway in microglia. However, the specificity role of P2X4R needs to be confirmed by more experiment.

Retinal diseases affect the health of millions of people worldwide and activated P2X7 receptors (P2X7Rs) are associated with the pathophysiology of a variety of retina-related diseases, including diabetic retinopathy, age-related macular degeneration, and glaucoma. Increasing evidence indicated that P2X7R is over-activated in retinopathy and is involved in the occurrence and development of diabetic retinopathy. Purine vasotoxicity caused by over-activation of P2X7R can lead to decreased retinal blood flow and vascular dysfunction and activation of P2X7R can lead to the production of a large number of inflammatory factors, causing local inflammatory cells to infiltrate and form a vascular microenvironment, thus constituting the pathophysiological basis for the occurrence and development of retinopathy. A variety of P2X7R antagonists have been studied in clinical trials as potential treatments for retinal diseases. However, currently no P2X7R antagonists has been approved for retina diseases. In this review, we mainly focus on recent progress on the involvement of P2X7R in retinal diseases and its therapeutic potential in the future.

Epilepsy is one of the most common chronic brain diseases affecting up to 70 million people worldwide. Major challenges of epilepsy treatment include the high pharmacoresistance in patients and the lack of disease-modification. Extracellular adenosine 3'triphosphate (ATP), a key neurotransmitter in the activation of the purinergic signalling system, is increasingly recognized to contribute to pathological brain hyperexcitability in epilepsy. Consequently, targeting ATP-release mechanisms may constitute a new therapeutic strategy for seizure control and epilepsy. The calcium channel, Calcium Homeostasis Modulator 1 (CALHM1), a voltage-gated, non-selective ion channel that permits the passage of various cations and small molecules, is expressed in neurons and plays an essential role during neuronal excitability and neurotransmission. In addition to ions, CALHM1 also allows the passage of ATP into the extracellular space, activating thereby purinergic receptors. Here, we tested if the pharmacological blocking of CALHM1 via CGP37157 (7-chloro-5-(2-chlorophenyl)-3,5-dihydro-4,1-benzothiazepin-2-(1H)-one) alters the severity of intra-amygdala kainic acid-induced status epilepticus. Our results show that CGP37157 increased the severity of seizures during status epilepticus. In addition, CALHM1 protein levels are down-regulated in the hippocampus in epileptic mice and Temporal Lobe Epilepsy (TLE) patients. In summary, our results identify CALHM1 as a new contributor to seizures and suggest targeting of CALHM1 as new treatment strategy for epilepsy.

This Journal Club article reviews a 2025 study by Qiu et al. that reports the development of a novel iodine-125 radioligand targeting the purinergic P2X7 receptor (P2X7R). The researchers created a small library of structurally modified P2X7R antagonists and identified compound 1c as a lead due to its high affinity and selectivity. Radiolabeling with iodine-125 produced [I]1c with high yield and purity. Binding studies confirmed its strong nanomolar affinity, supporting its use in radioligand screening and potential applications in imaging P2X7R in inflammatory and neurodegenerative diseases. The study demonstrates the value of radiolabeled probes in drug discovery and purinergic signaling research.