Transcriptomic alterations in APP/PS1 mice astrocytes lead to early postnatal axon initial segment structural changes.

Alzheimer´s disease (AD) is characterized by neuronal function loss and degeneration. The integrity of the axon initial segment (AIS) is essential to maintain neuronal function and output. AIS alterations are detected in human post-mortem AD brains and mice models, as well as, neurodevelopmental and mental disorders. However, the mechanisms leading to AIS deregulation in AD and the extrinsic glial origin are elusive. We studied early postnatal differences in AIS cellular/molecular mechanisms in wild-type or APP/PS1 mice and combined neuron-astrocyte co-cultures. We observed AIS integrity alterations, reduced ankyrinG expression and shortening, in APP/PS1 mice from P21 and loss of AIS integrity at 21 DIV in wild-type and APP/PS1 neurons in the presence of APP/PS1 astrocytes. AnkyrinG decrease is due to mRNAs and protein reduction of retinoic acid synthesis enzymes Rdh1 and Aldh1b1, as well as ADNP (Activity-dependent neuroprotective protein) in APP/PS1 astrocytes. This effect was mimicked by wild-type astrocytes expressing ADNP shRNA. In the presence of APP/PS1 astrocytes, wild-type neurons AIS is recovered by inhibition of retinoic acid degradation, and Adnp-derived NAP peptide (NAPVSIPQ) addition or P2X7 receptor inhibition, both regulated by retinoic acid levels. Moreover, P2X7 inhibitor treatment for 2 months impaired AIS disruption in APP/PS1 mice. Our findings extend current knowledge on AIS regulation, providing data to support the role of astrocytes in early postnatal AIS modulation. In conclusion, AD onset may be related to very early glial cell alterations that induce AIS and neuronal function changes, opening new therapeutic approaches to detect and avoid neuronal function loss.

Adenosine triphosphate release inhibitors targeting pannexin1 improve recovery after spinal cord injury.

Traumatic spinal cord injury is characterized by immediate and irreversible tissue loss at the lesion site and secondary tissue damage. Secondary injuries should, in principle, be preventable, although no effective treatment options currently exist for patients with acute spinal cord injury. Traumatized tissues release excessive amounts of adenosine triphosphate and activate the P2X purinoceptor 7/pannexin1 complex, which is associated with secondary injury. We investigated the neuroprotective effects of the blue dye Brilliant Blue FCF, a selective inhibitor of P2X purinoceptor 7/pannexin1 that is approved for use as a food coloring, by comparing it with Brilliant Blue G, a P2X7 purinoceptor antagonist, and carbenoxolone, which attenuates P2X purinoceptor 7/pannexin1 function, in a rat spinal cord injury model. Brilliant Blue FCF administered early after spinal cord injury reduced spinal cord anatomical damage and improved motor recovery without apparent toxicity. Brilliant Blue G had the highest effect on this neurological recovery, with Brilliant Blue FCF and carbenoxolone having comparable improvement. Furthermore, Brilliant Blue FCF administration reduced local astrocytic and microglial activation and neutrophil infiltration, and no differences in these histological effects were observed between compounds. Thus, Brilliant Blue FCF protects spinal cord neurons after spinal cord injury and suppresses local inflammatory responses as well as Brilliant Blue G and carbenoxolone.

P2X7 receptors modulate acquisition of cue fear extinction and contextual background memory generalization in male mice.

The purinergic P2X7 receptors (P2X7R) are activated by adenosine triphosphate (ATP) in several brain regions, particularly those involved with emotional control and the regulation of fear-related memories. Here, we investigate the role of P2X7R in fear learning memory, specifically in the acquisition and consolidation phases of the cued fear conditioning paradigm. C57Bl/6 wildtype (WT) male mice that received a single i.p. injection of the selective P2X7R antagonist A438079 prior the conditioning session showed generalization of cued fear memory and impaired fear extinction recall in the test session, while those treated prior the extinction session exhibited a similar behavior profile accompanied by resistance in the extinction learning. However, no effects were observed when this drug was administered immediately after the conditioning, extinction, or before the test session. Our results with P2X7R knockout (P2X7 KO) mice showed a behavioral profile that mirrored the collective effects observed across all pharmacological treatment conditions. This suggests that the P2X7R KO model effectively replicates the behavioral changes induced by the pharmacological interventions, demonstrating that we have successfully isolated the role of P2X7R in the fear and extinction phases of memory. These findings highlight the role of P2X7R in the acquisition and recall of extinction memory and supports P2X7R as a promising candidate for controlling abnormal fear processing, with potential applications for stress exposure-related disorders such as post-traumatic stress disorder (PTSD).

Druggable targets for Parkinson's disease: transcriptomics based Mendelian randomization study.

Parkinson's disease (PD) is a prevalent neurodegenerative disorder. Currently available drugs for PD, can only relieve the symptoms of PD, but cannot prevent the progression of the disease and have serious side effects. Other new druggable therapeutic targets for PD are needed. First, six GEO datasets with transcriptomic data from the substantia nigra (SN) region of the brain were downloaded to find dysregulated druggable genes in PD. Then, Mendelian randomization (MR) and summary statistics-based MR (SMR) analysis were conducted using eQTL data from both brain tissue and blood to investigate the relationship between gene expression and PD. Next, the association between the expression of candidate druggable targets and disease stage was validated in an additional dataset GSE49036. Finally, a phenome-wide MR analysis was carried out to investigate the potential impact of candidate druggable genes on several other complex diseases or traits. Our study revealed 313 differentially expressed genes that may be directly targetable and have an impact on PD (FDR-p < 0.1). Through MR and SMR analysis, P2RX7 and RNASET2 were identified as feasible PD therapeutic targets, which were highly expressed in PD tissues and increased as the Braak stages increased. Phenome-wide MR analysis revealed other effects of targeting RNASET2. This study presents genetic support for the potential therapeutic properties of targeting P2RX7 and RNASET2, which will be useful for developing druggable therapeutic targets for PD.

P2X7 receptors exhibit at least three modes of allosteric antagonism.

P2X receptors are trimeric ion channels activated by adenosine triphosphate (ATP) that contribute to pathophysiological processes ranging from asthma to neuropathic pain and neurodegeneration. A number of small-molecule antagonists have been identified for these important pharmaceutical targets. However, the molecular pharmacology of P2X receptors is poorly understood because of the chemically disparate nature of antagonists and their differential actions on the seven constituent subtypes. Here, we report high-resolution cryo-electron microscopy structures of the homomeric rat P2X7 receptor bound to five previously known small-molecule allosteric antagonists and a sixth antagonist that we identify. Our structural, biophysical, and electrophysiological data define the molecular determinants of allosteric antagonism in this pharmacologically relevant receptor, revealing three distinct classes of antagonists that we call shallow, deep, and starfish. Starfish binders, exemplified by the previously unidentified antagonist methyl blue, represent a unique class of inhibitors with distinct functional properties that could be exploited to develop potent P2X7 ligands with substantial clinical impact.

Persistent Activation of the P2X7 Receptor Underlies Chronic Inflammation and Carcinogenic Changes in the Intestine.

Aberrant signaling through damage-associated molecular patterns (DAMPs) has been linked to several health disorders, attracting considerable research interest over the last decade. Adenosine triphosphate (ATP), a key extracellular DAMP, activates the purinergic receptor P2X7, which acts as a danger sensor in immune cells and is implicated in distinct biological functions, including cell death, production of pro-inflammatory cytokines, and defense against microorganisms. In addition to driving inflammation mediated by immune and non-immune cells, the persistent release of endogenous DAMPs, including ATP, has been shown to result in epigenetic modifications. In intestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer (CRC), consequent amplification of the inflammatory response and the resulting epigenetic reprogramming may impact the development of pathological changes associated with specific disease phenotypes. P2X7 is overexpressed in the gut mucosa of patients with IBD, whereas the P2X7 blockade prevents the development of chemically induced experimental colitis. Recent data suggest a role for P2X7 in determining gut microbiota composition. Regulatory mechanisms downstream of the P2X7 receptor, combined with signals from dysbiotic microbiota, trigger intracellular signaling pathways and inflammasomes, intensify inflammation, and foster colitis-associated CRC development. Preliminary studies targeting the ATP-P2X7 pathway have shown favorable therapeutic effects in human IBD and experimental colitis.

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.

Discovery of a Potent, Orally Active, and Long-Lasting P2X7 Receptor Antagonist as a Preclinical Candidate for Delaying the Progression of Chronic Kidney Disease.

Chronic kidney disease (CKD) is a condition characterized by functional deterioration with sustained inflammation and progressive fibrosis of the kidneys affecting over 800 million people worldwide. The P2X7 receptor (P2X7R) plays a key role in CKD progression. Our previous P2X7R antagonists demonstrated good efficacy for treating kidney injury but were limited by low oral exposure and short half-life, restricting their application. This study reports the optimization of P2X7R antagonists for better oral pharmacokinetics. The candidate compound 13a with the respective IC50 of 34.86 and 25.28 nM against human and murine P2X7R, administered orally at 10 mg/kg in mice, exhibits a remarkably long half-life of 161.64 h, with a high exposure of 1,163,980.55 µg·h/L. Oral administration of 13a (0.3 or 1.0 mg/kg, twice weekly) significantly reduced renal injury and fibrosis in unilateral ureteral obstruction and adenine diet-induced mice models, highlighting its potential for delaying the progression of CKD.

Neuroinflammatory responses and blood-brain barrier injury in chronic alcohol exposure: role of purinergic P2 × 7 Receptor signaling.

Alcohol consumption leads to neuroinflammation and blood‒brain barrier (BBB) damage, resulting in neurological impairment. We previously demonstrated that ethanol-induced disruption of barrier function in human brain endothelial cells was associated with mitochondrial injury, increased ATP and extracellular vesicle (EV) release, and purinergic receptor P2 × 7R activation. Therefore, we aimed to evaluate the effect of P2 × 7R blockade on peripheral and neuro-inflammation in ethanol-exposed mice. In a chronic intermittent ethanol (CIE)-exposed mouse model, P2 × 7R was inhibited by two different methods: Brilliant Blue G (BBG) or gene knockout. We assessed blood ethanol concentration (BEC), brain microvessel gene expression by using RT2 PCR array, plasma P2 × 7R and P-gp, serum ATP, EV-ATP, number of EVs, and EV mtDNA copy numbers. An RT2 PCR array of brain microvessels revealed significant upregulation of proinflammatory genes involved in apoptosis, vasodilation, and platelet activation in CIE-exposed wild-type animals, which were decreased 15-50-fold in BBG-treated-CIE-exposed animals. Plasma P-gp levels and serum P2 × 7R shedding were significantly increased in CIE-exposed animals. Pharmacological or genetic suppression of P2 × 7R decreased receptor shedding to levels equivalent to those in control group. The increase in EV number and EV-ATP content in the CIE-exposed mice was significantly reduced by P2 × 7R inhibition. CIE mice showed augmented EV-mtDNA copy numbers which were reduced in EVs after P2 × 7R inhibition or receptor knockout. These observations suggested that P2 × 7R signaling plays a critical role in ethanol-induced brain injury. Increased extracellular ATP, EV-ATP, EV numbers, and EV-mtDNA copy numbers highlight a new mechanism of brain injury during alcohol exposure via P2 × 7R and biomarkers of such damage. In this study, for the first time, we report the in vivo involvement of P2 × 7R signaling in CIE-induced brain injury.

Casting NETs on Psoriasis: The modulation of inflammatory feedback targeting IL-36/IL-36R axis.

NETosis happens when neutrophils are activated and neutrophil extracellular traps (NETs) are formed synchronously, which is a hallmark of psoriasis. However, the specific trigger that drives NET formation and the distinct contents and interaction with interleukin-36 receptor (IL-36R) of NETs remain to be further elucidated. This work identified NET formation driven by toll-like receptor (TLR) 3 ligand (especially polyinosinic-polycytidylic acid (Poly(I:C)) were enhanced by purinergic receptor P2X ligand-gated ion channel 7 receptor (P2X7R) ligands (especially adenosine 5'-triphosphate (ATP)). NET formation was accompanied by the secretion of inflammatory cytokines and characterized by IL-1ß decoration. NET formation blockade decreased expressions of inflammatory cytokines and chemokines, which consequently improved inflammatory responses. Additionally, imiquimod (IMQ)-induced psoriasiform symptoms including neutrophilic infiltration tended to be time-sensitive. Mouse primary keratinocytes and mice deficient in Il1rl2, which encodes IL-36R, mitigated inflammatory responses and NET formation, thereby delaying the pathophysiology of psoriasis. Together, the findings provided the therapeutic potential for IL-36 targeting NET inhibitors in psoriasis treatment.

Exploring P2X receptor activity: A journey from cellular impact to electrophysiological profiling.

The development of in vitro pharmacological assays relies on creating genetically modified cell lines that overexpress the target protein of interest. However, the choice of the host cell line can significantly impact the experimental outcomes. This study explores the functional characterization of P2X7 and P2X4 receptor modulators through cellular assays and advanced electrophysiological techniques. The influence of different host cell lines (HEK-293, HEK-293FT, and 1321N1) on the activity of reference agonists and antagonists targeting human and murine P2X4 and P2X7 receptors was systematically investigated, highlighting the significant impact of the host cell on experimental results. The 1321N1 cell line was identified as the preferred host cell line when investigating the human P2X4 receptor due to more consistent agonist activities, antagonist potencies, and a more stable assay signal window. Furthermore, a patch-clamp protocol that allows for the repetitive recording of ATP-mediated inward currents from isolated human CD4+ T-cells was established, revealing that both P2X7 and P2X4 receptors are crucial for immune cell regulation, positioning them as promising therapeutic targets for managing inflammatory disorders.

P2X7 expression patterns in the developing Fmr1-knockout mouse hippocampus.

Fragile-X Syndrome (FXS) is the leading monogenetic cause of intellectual disability among children but remains without a cure. Using the Fmr1 KO mouse model of FXS, much work has been done to understand FXS hippocampus dysfunction. Purinergic signaling, where ATP and its metabolites are used as signaling molecules, participates in hippocampus development, but it is unknown if purinergic signaling is affected in the developing Fmr1 KO hippocampus. In our study, we characterized the purinergic receptor P2X7. We first found that P2X7 was reduced in Fmr1 KO whole hippocampus tissue at P14 and P21, corresponding to the periods of neurite outgrowth and synaptic refinement in the hippocampus. We then evaluated the cell-specific expression of P2X7 with immunofluorescence and found differences between WT and Fmr1 KO mice in P2X7 colocalization with hippocampal microglia and neurons. P2X7 colocalized more with microglia at P14 and P21, but there was a sex-specific reduction in P2X7 colocalization with neurons. In contrast, male mice at P14 and P21 showed reduced neuronal P2X7 colocalization compared to females, but only females showed reduced absolute neuronal P2X7 expression across the dorsal hippocampal formation. Together, our results suggest that P2X7 expression is altered during Fmr1-KO hippocampal development, potentially influencing several developmental processes in the Fmr1-KO hippocampus formation.

Inflammatory response and parasite regulation in acute toxoplasmosis: the role of P2X7 receptor in controlling virulent atypical genotype strain of Toxoplasma gondii.

Toxoplasmosis is a globally significant disease that poses a severe threat to immunocompromised individuals, especially in Brazil, where a high prevalence of virulent and atypical strains of Toxoplasma gondii is observed. In 1998, the EGS strain, exhibiting a unique infection phenotype, was isolated in Brazil, adding to the complexity of strain diversity. The P2X7 receptor is critical in inflammation and controlling intracellular microorganisms such as T. gondii. However, its genetic variability can result in receptor dysfunction, potentially worsening susceptibility. This study investigates the role of the P2X7 receptor during acute infection induced by the EGS atypical strain, offering insight into the mechanisms of T. gondii infection in this context. We infected the female C57BL/6 (WT) or P2X7 knockout (P2X7-/-) by gavage. The EGS infection causes intestinal inflammation. The P2X7-/- mice presented higher parasite load in the intestine, spleen, and liver. The absence of the P2X7 receptor disrupts inflammatory cell balance by reducing NLRP3, IL-1ß, and Foxp3 expression while increasing IFN-γ expression and production in the intestine. In the liver, P2X7-/- animals demonstrate diminished inflammatory infiltrate within the portal and lobular regions concurrent with an enlargement of the spleen. In conclusion, the infection of mice with the EGS strain elicited immune alterations, leading to acute inflammation and cytokine dysregulation, while the P2X7 receptor conferred protection against parasitic proliferation across multiple organs.

Quercetin Mitigates Lysophosphatidylcholine (LPC)-Induced Neutrophil Extracellular Traps (NETs) Formation through Inhibiting the P2X7R/P38MAPK/NOX2 Pathway.

Neutrophil extracellular traps (NETs) are three-dimensional reticular structures that release chromatin and cellular contents extracellularly upon neutrophil activation. As a novel effector mechanism of neutrophils, NETs possess the capacity to amplify localized inflammation and have been demonstrated to contribute to the exacerbation of various inflammatory diseases, including cardiovascular diseases and tumors. It is suggested that lysophosphatidylcholine (LPC), as the primary active component of oxidized low-density lipoprotein, represents a significant risk factor for various inflammatory diseases, such as cardiovascular diseases and neurodegenerative diseases. However, the specific mechanism of NETs formation induced by LPC remains unclear. Quercetin has garnered considerable attention due to its anti-inflammatory properties, serving as a prevalent flavonoid in daily diet. However, little is currently known about the underlying mechanisms by which quercetin inhibits NETs formation and alleviates associated diseases. In our study, we utilized LPC-treated primary rat neutrophils to establish an in vitro model of NETs formation, which was subsequently subjected to treatment with a combination of quercetin or relevant inhibitors/activators. Compared to the control group, the markers of NETs and the expression of P2X7R/P38MAPK/NOX2 pathway-associated proteins were significantly increased in cells treated with LPC alone. Quercetin intervention decreased the LPC-induced upregulation of the P2X7R/P38MAPK/NOX2 pathway and effectively reduced the expression of NETs markers. The results obtained using a P2X7R antagonist/activator and P38MAPK inhibitor/activator support these findings. In summary, quercetin reversed the upregulation of the LPC-induced P2X7R/P38MAPK/NOX2 pathway, further mitigating NETs formation. Our study investigated the potential mechanism of LPC-induced NETs formation, elucidated the inhibitory effect of quercetin on NETs formation, and offered new insights into the anti-inflammatory properties of quercetin.

Inhibition of P2RX7 contributes to cytotoxicity by suppression of glycolysis and AKT activation in human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer. HCC occurs people with chronic liver diseases. The purinergic receptor P2X 7 (P2RX7) is involved in tumor proliferation and growth. Also, P2RX7 is associated with tumor invasion and metastatic dissemination. High glucose utilization is important for the survival of various types of tumors. However, the role of P2RX7 in glucose metabolism and cellular survival of HCC remains unclear. Here, our results show that the gene and protein levels of P2RX7 were elevated in tumor cells of patients with HCC. The pharmacological inhibition of P2RX7 by A-804598, a selective P2RX7 antagonist, and genetic inhibition by P2RX7 knockdown suppressed the glycolytic activity by reduction of hexokinase 2 (HK2), a key enzyme of the glycolysis pathway, in human HCC cells. Also, both A-804598 treatment and P2RX7 knockdown induced cytotoxicity via inhibition of AKT activation which is critical for tumor cell survival in human HCC cells. Moreover, A-804598 treatment and P2RX7 knockdown increased cytotoxicity and caspase-3 activation in human HCC cells. These results suggest that inhibition of P2RX7 contributes to cytotoxicity by suppression of glycolysis and AKT activation in human HCC. [BMB Reports 2024; 57(10): 459-464].

Specnuezhenide ameliorates hepatic fibrosis via regulating SIRT6-Mediated inflammatory signaling cascades.

ETHNOPHARMACOLOGICAL RELEVANCE: Ligustrum lucidum W.T. Aiton is a traditional Chinese medicine that has long been used with high hepatoprotective therapeutic and condition value. Specnuezhenide (SP), the standard prominent secoiridoid compound of Fructus Ligustri Lucidi may ameliorate hepatic inflammation in chronic liver diseases. AIM OF THE STUDY: Regulating inflammation through SIRT6-P2X7R axis has caused the emergence of novel molecular mechanism strategies for reversing hepatic fibrosis. This study focused on the mechanism of SP in modulating the liver inflammatory microenvironment in hepatic fibrosis. MATERIALS AND METHODS: C57BL/6 mice with hepatic fibrosis were stimulated with thioacetamide (TAA) prior to administration of SP. Hepatic stellate cells (HSCs) or normal mouse primary hepatocytes were exposed to transforming growth factor-ß (TGF-ß) treatment. Meanwhile, normal mouse bone marrow-derived macrophages (BMDMs) were treated with lipopolysaccharide/adenosine triphosphate (LPS/ATP), aiming to obtain the conditioned medium. HSCs and hepatocytes were transfected with SIRT6 knockdown vector (siRNA-SIRT6) to estimate the impact of SP on the SIRT6-P2X7R/NLRP3 signaling pathway. RESULTS: SP suppressed the HSCs extracellular matrix (ECM) deposition as well as pro-inflammatory cytokine levels induced by the medium of BMDMs or TGF-ß. In addition, SP also significantly up-regulated SIRT6, inhibited P2X7R-NLRP3 inflammasome in HSCs and hepatocytes, and functioned as MDL-800 (a SIRT6 agonist). SP reduced the hepatocytes pyroptosis and further prevented the occurrence of inflammatory response in the liver. SP could inhibit the activation of BMDMs and impede IL-1ß and IL-18 from entering extracellular regions. Moreover, deficiency of SIRT6 in HSCs or hepatocytes reduced SP's regulation of P2X7R suppression. For TAA-treated mice, SP mitigated histopathological changes, ECM accumulation, EMT process, and NETs formation in hepatic fibrosis. CONCLUSIONS: Therefore, SP decreased inflammatory response via SIRT6-P2X7R/NLRP3 pathway and suppressed fibrillogenesis. These findings supported SP as the novel candidate to treat hepatic fibrosis.

Diverse calcium signaling profiles regulate migratory behavior in avascular wound healing and aberrant signal hierarchy occurs early in diabetes.

In avascular wound repair, calcium signaling events are the predominant mechanism cells use to transduce information about stressors in the environment into an effective and coordinated migratory response. Live cell imaging and computational analysis of corneal epithelial wound healing revealed that signal initiation and propagation at the wound edge are highly ordered, with groups of cells engaging in cyclical patterns of initiation and propagation. The cells in these groups exhibit a diverse range of signaling behavior, and dominant "conductor cells" drive activity in groups of lower-signaling neighbors. Ex vivo model systems reveal that conductor cells are present in wing cell layers of the corneal epithelium and that signaling propagates both within and between wing and basal layers. There are significant aberrations in conductor phenotype and interlayer propagation in type II diabetic murine models, indicating that signal hierarchy breakdown is an early indicator of disease. In vitro models reveal that signaling profile diversity and conductor cell phenotype is eliminated with P2X7 inhibition and is altered in Pannexin-1 or P2Y2 but not Connexin-43 inhibition. Conductor cells express significantly less P2X7 than their lower-signaling neighbors and exhibit significantly less migratory behavior after injury. Together, our results show that the postinjury calcium signaling cascade exhibits significantly more ordered and hierarchical behavior than previously thought, that proteins previously shown to be essential for regulating motility are also essential for determining signaling phenotype, and that loss of signal hierarchy integrity is an early indicator of disease state. NEW & NOTEWORTHY Calcium signaling in corneal epithelial cells after injury is highly ordered, with groups of cells engaged in cyclical patterns of event initiation and propagation driven by high-signaling cells. Signaling behavior is determined by P2X7, Pannexin-1, and P2Y2 and influences migratory behavior. Signal hierarchy is observed in healthy ex vivo models after injury and becomes aberrant in diabetes. This represents a paradigm shift, as signaling was thought to be random and determined by factors in the environment.

Reduction of TRPV1 expression on neurons due to downregulation of P2X7R in neonatal rat dorsal root ganglion satellite glial cells under co-culture conditions.

BACKGROUND INFORMATION: The purinergic ligand-gated ion channel 7 receptor (P2X7R) is an ATP-gated ion channel that transmits extracellular signals and induces corresponding biological effects, transient receptor potential vanilloid type 1 (TRPV1) is a non-selective cation channel that maintains normal physiological functions; numerous studies showed that P2X7R and TRPV1 are associated with inflammatory reactions. RESULTS: The effect of P2X7R knockdown in satellite glial cells (SGCs) on neuronal TRPV1 expression under high glucose and high free fat (HGHF) environment was investigated. P2X7 short hairpin RNA (shRNA) was utilized to downregulate P2X7R in SGCs, and treated and untreated SGCs were co-cultured with neuronal cell lines. The expression levels of inflammatory factors and signaling pathways in SGCs and neurons were measured using Western blot analysis, RT-qPCR, immunofluorescence, and enzyme-linked immunosorbent assays. Results suggested that P2X7 shRNA reduced the expression levels of P2X7R protein and mRNA in SGCs surrounding DRG neurons and downregulated the release of tumor necrosis factor-alpha and interleukin-1 beta via the Ca2+/p38 MAPK/NF-κB pathway. Additionally, the downregulation of P2X7R might decrease TRPV1 expression in neurons via the Ca2+/PKC-ɛ/p38 MAPK pathway. CONCLUSIONS: Reducing P2X7R expression in SCGs in an HGHF environment could decrease neuronal TRPV1 expression via the Ca2+/PKC-ɛ/p38 MAPK pathway.

High-affinity agonism at the P2X7 receptor is mediated by three residues outside the orthosteric pocket.

P2X receptors are trimeric ATP-gated ion channels that activate diverse signaling cascades. Due to its role in apoptotic pathways, selective activation of P2X7 is a potential experimental tool and therapeutic approach in cancer biology. However, mechanisms of high-affinity P2X7 activation have not been defined. We report high-resolution cryo-EM structures of wild-type rat P2X7 bound to the high-affinity agonist BzATP as well as significantly improved apo receptor structures in the presence and absence of sodium. Apo structures define molecular details of pore architecture and reveal how a partially hydrated Na+ ion interacts with the conductance pathway in the closed state. Structural, electrophysiological, and direct binding data of BzATP reveal that three residues just outside the orthosteric ATP-binding site are responsible for its high-affinity agonism. This work provides insights into high-affinity agonism for any P2X receptor and lays the groundwork for development of subtype-specific agonists applicable to cancer therapeutics.