Different localization of P2X4 and P2X7 receptors in native mouse lung - lack of evidence for a direct P2X4-P2X7 receptor interaction.

Introduction: P2X receptors are a family of homo- and heterotrimeric cation channels gated by extracellular ATP. The P2X4 and P2X7 subunits show overlapping expression patterns and have been involved in similar physiological processes, such as pain and inflammation as well as various immune cell functions. While formation of P2X2/P2X3 heterotrimers produces a distinct pharmacological phenotype and has been well established, functional identification of a P2X4/P2X7 heteromer has been difficult and evidence for and against a physical association has been found. Most of this evidence stems, however, from in vitro model systems. Methods: Here, we used a P2X7-EGFP BAC transgenic mouse model as well as P2X4 and P2X7 knock-out mice to re-investigate a P2X4-P2X7 interaction in mouse lung by biochemical and immunohistochemical experiments as well as quantitative expression analysis. Results: No detectable amounts of P2X4 could be co-purified from mouse lung via P2X7-EGFP. In agreement with these findings, immuno-histochemical analysis using a P2X7-specific nanobody revealed only limited overlap in the cellular and subcellular localizations of P2X4 and P2X7 in both the native lung tissue and primary cells. Comparison of P2X4 and P2X7 transcript and protein levels in the respective gene-deficient and wild type mice showed no mutual interrelation between their expression levels in whole lungs. However, a significantly reduced P2rx7 expression was found in alveolar macrophages of P2rx4 -/- mice. Discussion: In summary, our detailed analysis of the cellular and subcellular P2X4 and P2X7 localization and expression does not support a physiologically relevant direct association of P2X4 and P2X7 subunits or receptors in vivo.

Electroacupuncture improves allodynia and central sensitization via modulation of microglial activation associated P2X4R and inflammation in a rat model of migraine.

Background: Recent studies have demonstrated that activated microglia were involved in the pathogenesis of central sensitization characterized by cutaneous allodynia in migraine. Activation of microglia is accompanied by increased expression of its receptors and release of inflammatory mediators. Acupuncture and its developed electroacupuncture (EA) have been recommended as an alternative therapy for migraine and are widely used for relieving migraine-associated pain. However, it remains rare studies that show whether EA exerts anti-migraine effects via inhibiting microglial activation related to a release of microglial receptors and the inflammatory pathway. Therefore, this study aimed to investigate EA' ability to ameliorate central sensitization via modulation of microglial activation, microglial receptor, and inflammatory response using a rat model of migraine induced by repeated epidural chemical stimulation. Methods: In the present study, a rat model of migraine was established by epidural repeated inflammatory soup (IS) stimulation and treated with EA at Fengchi (GB20) and Yanglingquan (GB34) and acupuncture at sham-acupoints. Pain hypersensitivity was further determined by measuring the mechanical withdrawal threshold using the von-Frey filament. The changes in c-Fos and ionized calcium binding adaptor molecule 1 (Ibal-1) labeled microglia in the trigeminal nucleus caudalis (TNC) were examined by immunflurescence to assess the central sensitization and whether accompanied with microglia activation. In addition, the expression of Ibal-1, microglial purinoceptor P2X4, and its associated inflammatory signaling pathway mediators, including interleukin (IL)-1ß, NOD-like receptor protein 3 (NLRP3), and Caspase-1 in the TNC were investigated by western blot and real-time polymerase chain reaction analysis. Results: Allodynia increased of c-Fos, and activated microglia were observed after repeated IS stimulation. EA alleviated the decrease in mechanical withdrawal thresholds, reduced the activation of c-Fos and microglia labeled with Ibal-1, downregulated the level of microglial purinoceptor P2X4, and limited the inflammatory response (NLRP3/Caspase-1/IL-1ß signaling pathway) in the TNC of migraine rat model. Conclusions: Our results indicate that the anti-hyperalgesia effects of EA ameliorate central sensitization in IS-induced migraine by regulating microglial activation related to P2X4R and NLRP3/IL-1ß inflammatory pathway.

P2X7R and P2X4R expression of mice submandibular gland in high-fat diet/streptozotocin-induced type 2 diabetes.

Type 2 diabetes mellitus (T2DM) is a chronic inflammatory disease that can compromise the functioning of various organs, including the salivary glands (SG). The purinergic system is one of the most important inflammatory pathways in T2DM condition, and P2X7R and P2X4R are the primary purinergic receptors in SG that regulate inflammatory homeostasis. This study aimed to evaluate P2X7R and P2X4R expression, and morphological changes in the submandibular gland (SMG) in T2DM. Twenty-four 5-week-old mice were randomly assigned to control (CON) and diabetes mellitus (DM) groups (n = 12 each). Body weight, diet, and blood glucose levels were monitored weekly. The histomorphology of the SMG and the expression of the P2X7R, and P2X7R was evaluated by immunohistochemistry (IHC) staining and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) at 11 and 13 weeks of age. Our findings indicate a significant increase in food consumption, body weight, and blood glucose levels in the DM group. Although a significant increase in P2X7R and P2X4R expression was observed in the DM groups, the receptor location remained unchanged. We also observed a significant increase in the acinar area in the DM13w group, and a significant decrease in the ductal area in the DM11w and DM13w groups. Targeting purinergic receptors may offer novel therapeutic methods for diabetic complications.

Endothelin-1-mediated Brainstem Glial Activation Produces Asthmatic Airway Vagal Hypertonia Via Enhanced ATP-P2X4 Receptor Signaling in Sprague-Dawley Rats.

The occurrence of major asthma symptoms is largely attributed to airway vagal hypertonia, of which the central mechanisms remain unclear. This study tests the hypotheses that endothelin-1-mediated brainstem glial activation produces asthmatic airway vagal hypertonia via enhanced action of adenosine 5'-triphosphate on neuronal purinergic P2X4 receptors. A rat model of asthma was prepared using ovalbumin. Airway vagal tone was evaluated by the recurrent laryngeal discharge and plethysmographic measurement of pulmonary function. The changes in the brainstem were examined using ELISA, Western blot, luciferin-luciferase, quantitative reverse transcription-polymerase chain reaction, enzyme activity assay and immunofluorescent staining, respectively. The results showed that in the medulla of rats, endothelin receptor type B and P2X4 receptors were primarily expressed in astrocytes and neurons, respectively, and both of which, along with endothelin-1 content, were significantly increased after ovalbumin sensitization. Ovalbumin sensitization significantly increased recurrent laryngeal discharge, which was blocked by acute intracisternal injection of P2X4 receptor antagonist 5-BDBD, knockdown of brainstem P2X4 receptors, and chronic intraperitoneal injection of endothelin receptor type B antagonist BQ788, respectively. Ovalbumin sensitization activated microglia and astrocytes and significantly decreased ecto-5'-nucleotidase activity in the medulla, and all of which, together with the increase of medullary P2X4 receptor expression and decrease of pulmonary function, were reversed by chronic BQ788 treatment. These results demonstrated that in rats, allergic airway challenge activates both microglia and astrocytes in the medulla via enhanced endothelin-1/endothelin receptor type B signaling, which subsequently causes airway vagal hypertonia via augmented adenosine 5'-triphosphate/P2X4 receptor signaling in central neurons of airway vagal reflex.

Is there a biochemical basis for purinergic P2X3 and P2X4 receptor antagonists to be considered as anti-seizure medications?

Patients with epilepsy require improved medications. Purinergic receptors were identified as late as 1976 and are slowly emerging as potential drug targets for the discovery of antiseizure medications. While compounds interacting with these receptors have been approved for use as medicines (e.g., gefapixant for cough) and continue to be explored for a number of diseases (e.g., pain, cancer), there have been no purinergic receptor antagonists that have been advanced for epilepsy. There are very few studies on the channel conducting receptors, P2X3 and P2X4, that suggest their possible role in seizure generation or control. However, the limited data available provides some compelling reasons to believe that they could be valuable antiseizure medication drug targets. The data implicating P2X3 and P2X4 receptors in epilepsy includes the role played by ATP in neuronal excitability and seizures, receptor localization, increased receptor expression in epileptic brain, the involvement of these receptors in seizure-associated inflammation, crosstalk between these purinergic receptors and neuronal processes involved in seizures (GABAergic and glutamatergic neurotransmission), and the significant attenuation of seizures and seizure-like activity with P2X receptor blockade. The discovery of new and selective antagonists for P2X3 and P2X4 receptors is ongoing, armed with new structural data to guide rational design. The availability of safe, brain-penetrant compounds will likely encourage the clinical exploration of epilepsy as a disease entity.

Deficiency of purinergic P2X4 receptor alleviates experimental autoimmune hepatitis in mice.

Purinergic P2X4 receptor (P2X4R) has been shown to have immunomodulatory properties in infection, inflammation, and organ damage including liver regeneration and fibrosis. However, the mechanisms and pathophysiology associated with P2X4R during acute liver injury remain unknown. We used P2X4R-/- mice to explore the role of P2X4R in three different models of acute liver injury caused by concanavalin A (ConA), carbon tetrachloride, and acetaminophen. ConA treatment results in an increased expression of P2X4R in the liver of mice, which was positively correlated with higher levels of aspartate aminotransferase and alanine aminotransferase in the serum. However, P2X4R gene ablation significantly reduced the severity of acute hepatitis in mice caused by ConA, but not by carbon tetrachloride or acetaminophen. The protective benefits against immune-mediated acute hepatitis were achieved via modulating inflammation (Interleukin (IL)-1ß, IL-6, IL-17A, interferon-γ, tumor necrosis factor-α), oxidative stress (malondialdehyde, superoxide dismutase, glutathione peroxidase, and catalase), apoptosis markers (Bax, Bcl-2, and Caspase-3), autophagy biomarkers (LC3, Beclin-1, and p62), and nucleotide oligomerization domain-likereceptorprotein 3(NLRP3) inflammasome-activated pyroptosis markers (NLRP3, Gasdermin D, Caspase-1, ASC, IL-1ß). Additionally, administration of P2X4R antagonist (5-BDBD) or agonist (cytidine 5'-triphosphate) either improved or worsened ConA-induced autoimmune hepatitis, respectively. This study is the first to reveal that the absence of the P2X4 receptor may mitigate immune-mediated liver damage, potentially by restraining inflammation, oxidation, and programmed cell death mechanisms. And highlight P2X4 receptor is essential for ConA-induced acute hepatitis.

Methods for studying P2X4 receptor ion channels in immune cells.

The P2X4 receptor is a trimeric ligand-gated ion channel activated by adenosine 5'-triphosphate (ATP). P2X4 is present in immune cells with emerging roles in inflammation and immunity, and related disorders. This review aims to provide an overview of the methods commonly used to study P2X4 in immune cells, focusing on those methods used to assess P2RX4 gene expression, the presence of the P2X4 protein, and P2X4 ion channel activity in these cells from humans, dogs, mice and rats. P2RX4 gene expression in immune cells is commonly assessed using semi-quantitative and quantitative reverse-transcriptase-PCR. The presence of P2X4 protein in immune cells is mainly assessed using anti-P2X4 polyclonal antibodies with immunoblotting or immunochemistry, but the use of these antibodies, as well as monoclonal antibodies and nanobodies to detect P2X4 with flow cytometry is increasing. Notably, use of an anti-P2X4 monoclonal antibody and flow cytometry has revealed that P2X4 is present on immune cells with a rank order of expression in eosinophils, then neutrophils and monocytes, then basophils and B cells, and finally T cells. P2X4 ion channel activity has been assessed mainly by Ca2+ flux assays using the cell permeable Ca2+-sensitive dyes Fura-2 and Fluo-4 with fluorescence microscopy, spectrophotometry, or flow cytometry. However, other methods including electrophysiology, and fluorescence assays measuring Na+ flux (using sodium green tetra-acetate) and dye uptake (using YO-PRO-12+) have been applied. Collectively, these methods have demonstrated the presence of functional P2X4 in monocytes and macrophages, microglia, eosinophils, mast cells and CD4+ T cells, with other evidence suggestive of functional P2X4 in dendritic cells, neutrophils, B cells and CD8+ T cells.

Bone marrow plasma cells require P2RX4 to sense extracellular ATP.

Plasma cells produce large quantities of antibodies and so play essential roles in immune protection1. Plasma cells, including a long-lived subset, reside in the bone marrow where they depend on poorly defined microenvironment-linked survival signals1. We show that bone marrow plasma cells use the ligand-gated purinergic ion channel P2RX4 to sense extracellular ATP released by bone marrow osteoblasts through the gap-junction protein pannexin 3 (PANX3). Mutation of Panx3 or P2rx4 each caused decreased serum antibodies and selective loss of bone marrow plasma cells. Compared to their wild-type counterparts, PANX3-null osteoblasts secreted less extracellular ATP and failed to support plasma cells in vitro. The P2RX4-specific inhibitor 5-BDBD abrogated the impact of extracellular ATP on bone marrow plasma cells in vitro, depleted bone marrow plasma cells in vivo and reduced pre-induced antigen-specific serum antibody titre with little posttreatment rebound. P2RX4 blockade also reduced autoantibody titre and kidney disease in two mouse models of humoral autoimmunity. P2RX4 promotes plasma cell survival by regulating endoplasmic reticulum homeostasis, as short-term P2RX4 blockade caused accumulation of endoplasmic reticulum stress-associated regulatory proteins including ATF4 and B-lineage mutation of the pro-apoptotic ATF4 target Chop prevented bone marrow plasma cell demise on P2RX4 inhibition. Thus, generating mature protective and pathogenic plasma cells requires P2RX4 signalling controlled by PANX3-regulated extracellular ATP release from bone marrow niche cells.

[Enhancement of mast cells activation by ATP via P2X4 receptor].

Adenosine-5'-triphosphate (ATP) is an important intracellular energy currency, but it is released extracellularly in response to various stimuli and acts as an intercellular signaling molecule by stimulating various P2 receptors. ATP and ADP are stored in synaptic vesicles and secretory granules, and are released extracellularly upon stimulation, playing important roles in neurotransmission and platelet aggregation. Furthermore, considerable amount of ATP is released by mechanical stimuli such as skin scraping or by cell damage, which in turn activates immune cells to promote inflammatory responses. Mast cells (MCs) are derived from hematopoietic stem cells and play a central role in type I allergic reactions. MCs are activated by IgE-mediated antigen recognition, leading to type I allergic reactions. MCs express P2X7 receptors that are activated by high concentrations of ATP (>0.5 |mM), and reported to aggravate inflammatory bowel disease and dermatitis. In contrast, role of MC P2 receptors that respond to lower concentrations of ATP remains to be investigated. We investigated in detail the effects of ATP in mouse bone marrow-derived MCs, and found that lower concentrations of ATP (<100 |µM) promotes IgE-dependent and GPCR-mediated degranulation via the ionotropic P2X4 receptor. In mouse allergic models, P2X4 receptor signal promote MC-mediated allergic responses through comprehensively increasing the sensitivity of MCs to different stimuli. Since ATP is known to be released from various cells upon mechanical stimuli such as cell damage or scratching, inhibition of P2X4 receptor signaling may represent a novel strategy to abrogate allergic reaction.

Calcimycin mediates apoptosis in breast and cervical cancer cell lines by inducing intracellular calcium levels in a P2RX4-dependent manner.

BACKGROUND: Calcimycin (A23187) is a polyether antibiotic and divalent cation ionophore, extracted from Streptomyces chartrecensis. With wide variety of antimicrobial activities, it also exhibits cytotoxicity of tumor cells. Calcimycin exhibit therapeutic potential against tumor cell growth; however, the molecular mechanism remains to be fully elucidated. Present study explores the mechanism of calcimycin-induced apoptosis cancer cell lines. METHODS: Apoptotic induction in a dose-dependent manner were recorded with MTT assays, Phase contrast imaging, wound healing assay, fluorescence imaging by DAPI and AO/EB staining and FACS using cell line model. Mitochondrial potential was analyzed by TMRM assay as Ca2+ signaling is well known to be influenced and synchronized by mitochondria also. RESULTS: Calcimycin induces apoptosis in dose dependent manner, also accompanied by increased intracellular calcium-level and expression of purinergic receptor-P2RX4, a ligand-gated ion channel. CONCLUSION: Calcimycin tends to increase the intracellular calcium level, mRNA expression of ATP receptor P2RX4, and phosphorylation of p38. Blocking of either intracellular calcium by BAPTA-AM, P2RX4 expression by antagonist 5-BDBD, and phospho-p38 by SB203580, abrogated the apoptotic activity of calcimycin. GENERAL SIGNIFICANCE: Taken together, these results show that calcimycin induces apoptosis in P2RX4 and ATP mediated intracellular Ca2+ and p38 MAPK mediated pathway in both the cancer cell lines. This study explored a new mode of action for calcimycin in cancer that could be potentially employed in future studies for cancer therapeutic research. This study disentangles that the calcimycin-induced apoptotic cell death is P2RX4 and ATP involved, intracellular Ca2+ and p38 MAPK mediated pathway.

Extracellular vesicles from oral mucosa stem cells promote lipid raft formation in human microglia through TLR4, P2X4R, and αVß3/αVß5 signaling pathways.

Targeting of disease-associated microglia represents a promising therapeutic approach that can be used for the prevention or slowing down neurodegeneration. In this regard, the use of extracellular vesicles (EVs) represents a promising therapeutic approach. However, the molecular mechanisms by which EVs regulate microglial responses remain poorly understood. In the present study, we used EVs derived from human oral mucosa stem cells (OMSCs) to investigate the effects on the lipid raft formation and the phagocytic response of human microglial cells. Lipid raft labeling with fluorescent cholera toxin subunit B conjugates revealed that both EVs and lipopolysaccharide (LPS) by more than two times increased lipid raft formation in human microglia. By contrast, combined treatment with LPS and EVs significantly decreased lipid raft formation indicating possible interference of EVs with the process of LPS-induced lipid raft formation. Specific inhibition of Toll-like receptor 4 (TLR4) with anti-TLR4 antibody as well as inhibition of purinergic P2X4 receptor (P2X4R) with selective antagonist 5-BDBD inhibited EVs- and LPS-induced lipid raft formation. Selective blockage of αvß3/αvß5 integrins with cilengitide suppressed EV- and LPS-induced lipid raft formation in microglia. Furthermore, inhibition of TLR4 and P2X4R prevented EV-induced phagocytic activity of human microglial cells. We demonstrate that EVs induce lipid raft formation in human microglia through interaction with TLR4, P2X4R, and αVß3/αVß5 signaling pathways. Our results provide new insights about the molecular mechanisms regulating EV/microglia interactions and could be used for the development of new therapeutic strategies against neurological disorders.

Naringin inhibits P2X4 receptor expression on satellite glial cells in the neonatal rat dorsal root ganglion.

Naringin inhibits inflammation and oxidative stress, the P2 purinoreceptor X4 receptor (P2X4R) is associated with glial cell activation and inflammation, the purpose of this study is to investigate the effects of naringin on P2X4 receptor expression on satellite glial cells (SGCs) and its possible mechanisms. ATP promoted the SGC activation and upregulated P2X4R expression; naringin inhibited SGC activation, decreased expression of P2X4R, P38 MAPK/ERK, and NF-κB, and reduced levels of Ca2+, TNF-α, and IL-1ß in SGCs in an ATP-containing environment. These findings suggest that naringin attenuates the ATP-induced SGC activation and reduces P2X4R expression via the Ca2+-P38 MAPK/ERK-NF-κB pathway.

Structural insights into the allosteric inhibition of P2X4 receptors.

P2X receptors are ATP-activated cation channels, and the P2X4 subtype plays important roles in the immune system and the central nervous system, particularly in neuropathic pain. Therefore, P2X4 receptors are of increasing interest as potential drug targets. Here, we report the cryo-EM structures of the zebrafish P2X4 receptor in complex with two P2X4 subtype-specific antagonists, BX430 and BAY-1797. Both antagonists bind to the same allosteric site located at the subunit interface at the top of the extracellular domain. Structure-based mutational analysis by electrophysiology identified the important residues for the allosteric inhibition of both zebrafish and human P2X4 receptors. Structural comparison revealed the ligand-dependent structural rearrangement of the binding pocket to stabilize the binding of allosteric modulators, which in turn would prevent the structural changes of the extracellular domain associated with channel activation. Furthermore, comparison with the previously reported P2X structures of other subtypes provided mechanistic insights into subtype-specific allosteric inhibition.

Purinergic neurotransmission receptor P2X4 silencing alleviates intracerebral hemorrhage-induced neuroinflammation by blocking the NLRP1/Caspase-1 pathway.

This study is performed to explore the role of P2X4 in intracerebral hemorrhage (ICH) and the association between P2X4 and the NLRP1/Caspase-1 pathway. The mouse ICH model was established via collagenase injection into the right basal ganglia. P2X4 expression in brain tissues was knocked down via intracerebroventricular injection with adeno-associated virus (AAV) harboring shRNA against shP2X4. The gene expression of P2X4 and protein levels related to NLRP1 inflammasome were detected using qRT-PCR and Western blot analysis, respectively. Muramyl dipeptide (an activator of NLRP1) was used to activate NLRP1 in brain tissues. ICH induced high expression of P2X4 in mouse brain tissues. The knockdown of P2X4 alleviated short- and long-term neurological deficits of ICH mice, as well as inhibited the tissue expression and serum levels of pro-inflammatory cytokines, including TNF-α, interleukin (IL)-6, and IL-1ß. Additionally, the expressions of NLRP1, ASC, and pro-Caspase-1 were down-regulated upon P2X4 silencing. Moreover, neurological impairment and the expression and secretion of cytokines after P2X4 silencing were aggravated by the additional administration of MDP. P2X4 knockdown represses neuroinflammation in brain tissues after ICH. Mechanistically, P2X4 inhibition exerts a neuroprotective effect in ICH by blocking the NLRP1/Caspase-1 pathway.

Transcriptomic analysis reveals novel age-independent immunomodulatory proteins as a mode of cerebroprotection in P2X4 receptor knockout mice after ischemic stroke.

Identification of new potential drug target proteins and their plausible mechanisms for stroke treatment is critically needed. We previously showed that genetic deletion and short-term pharmacological inhibition of P2X4, a purinergic receptor for adenosine triphosphate (ATP), provides acute cerebroprotection. However, potential mechanisms remain unknown. Therefore, we employed RNA-Seq technology to identify the gene expression profiles and pathway analysis followed by qPCR validation of differentially expressed genes (DEGs). This analysis identified roles of DEGs in certain biological processes responsible for P2X4R-dependent cerebroprotection after stroke. We subjected both young and aged male and female global P2X4 receptor knock out (P2X4RKO) and littermate WT (WT) mice to ischemic stroke. After three days, mice were sacrificed, and total RNA was isolated using Trizol and subjected to RNA-Seq and NanoString-mediated qPCR. DESeq2, Gene Ontology (GO), and Ingenuity Pathway Analysis (IPA) were used to identify gene expression profiles and biological pathways. We found 2246 DEGs in P2X4R KO vs. WT tissue after stroke. Out of these DEGs, 1920 genes were downregulated and 325 genes were upregulated in P2X4R KO. GO/IPA analysis of the top 300 DEGs suggests an enrichment of inflammation and extracellular matrix component genes. qPCR validation of the top 30 DEGs revealed downregulation of two common age-independent genes in P2X4R KO mice: Interleukin-6 (Il-6), an inflammatory cytokine, and Cytotoxic T Lymphocyte-Associated Protein 2 alpha (Ctla2a), an immunosuppressive factor. These data suggest that P2X4R-mediated cerebroprotection after stroke is initiated by attenuation of immune modulatory pathways in both young and aged mice of both sexes.

Fast green FCF prevents postoperative cognitive dysfunction via the downregulation of the P2X4 receptor in mice.

Postoperative cognitive dysfunction (POCD) is a decline in cognitive function affecting the mental health of aged patients after surgery. The pathological mechanisms underlying POCD have not yet been clarified. The overexpression of the P2X4 receptor in the central nervous system (CNS) was reported to be associated with the onset of POCD. Fast green FCF (FGF), a widely used food dye, could decrease the expression of the P2X4 receptor in the CNS. This study aimed to explore whether FGF could prevent POCD via the down-regulation of CNS P2X4 receptor. Exploratory laparotomy under the anesthesia of fentanyl and droperidol was carried to establish an animal model of POCD in 10-12-months-olds mice. FGF significantly attenuated cognitive impairments and down-regulated the expression of the P2X4 receptor induced by surgery in mice. Moreover, the blockade of CNS P2X4 receptor by intrahippocampal injection of 5-BDBD induced cognitive-enhancing effects on POCD mice. In addition, the effects of FGF were abolished by ivermectin, which is a positive allosteric modulator of the P2X4 receptor. FGF also inhibited M1 polarization of microglia cells, decreased the phosphorylation of nuclear factor-κB (NF-κB), and reduced the production of pro-inflammatory cytokines. These results suggested that FGF produced anti-POCD cognitive-enhancing effects via down-regulation of the P2X4 receptor-associated neuroinflammation, providing a support that FGF might be a potential treatment for POCD.

Therapeutic targeting of P2X4 receptor and mitochondrial metabolism in clear cell renal carcinoma models.

BACKGROUND: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cancer. Large-scale metabolomic data have associated metabolic alterations with the pathogenesis and progression of renal carcinoma and have correlated mitochondrial activity with poor survival in a subset of patients. The aim of this study was to determine whether targeting mitochondria-lysosome interaction could be a novel therapeutic approach using patient-derived organoids as avatar for drug response. METHODS: RNAseq data analysis and immunohistochemistry were used to show overexpression of Purinergic receptor 4 (P2XR4) in clear cell carcinomas. Seahorse experiments, immunofluorescence and fluorescence cell sorting were used to demonstrate that P2XR4 regulates mitochondrial activity and the balance of radical oxygen species. Pharmacological inhibitors and genetic silencing promoted lysosomal damage, calcium overload in mitochondria and cell death via both necrosis and apoptosis. Finally, we established patient-derived organoids and murine xenograft models to investigate the antitumor effect of P2XR4 inhibition using imaging drug screening, viability assay and immunohistochemistry. RESULTS: Our data suggest that oxo-phosphorylation is the main source of tumor-derived ATP in a subset of ccRCC cells expressing P2XR4, which exerts a critical impact on tumor energy metabolism and mitochondrial activity. Prolonged mitochondrial failure induced by pharmacological inhibition or P2XR4 silencing was associated with increased oxygen radical species, changes in mitochondrial permeability (i.e., opening of the transition pore complex, dissipation of membrane potential, and calcium overload). Interestingly, higher mitochondrial activity in patient derived organoids was associated with greater sensitivity to P2XR4 inhibition and tumor reduction in a xenograft model. CONCLUSION: Overall, our results suggest that the perturbed balance between lysosomal integrity and mitochondrial activity induced by P2XR4 inhibition may represent a new therapeutic strategy for a subset of patients with renal carcinoma and that individualized organoids may be help to predict drug efficacy.

Crosstalking interactions between P2X4 and 5-HT3A receptors.

Ionotropic receptors are ligand-gated ion channels triggering fast neurotransmitter responses. Among them, P2X and 5-HT3 receptors have been shown to physically interact each other and functionally inducing cross inhibitory responses. Nevertheless, despite the importance of P2X4 and 5-HT3A receptors that mediate for example neuropathic pain and psychosis respectively, complementary evidence has recently started to move forward in the understanding of this interaction. In this review, we discuss current evidence supporting the mechanism of crosstalking between both receptors, from the structural to the transduction pathway level. We expect this work may guide the design of further experiments to obtain a comprehensive view for the neuropharmacological role of these interacting receptors. This article is part of the Special Issue on "The receptor-receptor interaction as a new target for therapy".

Microglial P2X4 receptors promote ApoE degradation and contribute to memory deficits in Alzheimer's disease.

Numerous evidences support that microglia contributes to the progression of Alzheimer's disease. P2X4 receptors are ATP-gated channels with high calcium permeability, which are de novo expressed in a subset of reactive microglia associated with various pathological contexts, contributing to microglial functions. P2X4 receptors are mainly localized in lysosomes and trafficking to the plasma membrane is tightly regulated. Here, we investigated the role of P2X4 in the context of Alzheimer's disease (AD). Using proteomics, we identified Apolipoprotein E (ApoE) as a specific P2X4 interacting protein. We found that P2X4 regulates lysosomal cathepsin B (CatB) activity promoting ApoE degradation; P2rX4 deletion results in higher amounts of intracellular and secreted ApoE in both bone-marrow-derived macrophage (BMDM) and microglia from APPswe/PSEN1dE9 brain. In both human AD brain and APP/PS1 mice, P2X4 and ApoE are almost exclusively expressed in plaque-associated microglia. In 12-month-old APP/PS1 mice, genetic deletion of P2rX4 reverses topographical and spatial memory impairment and reduces amount of soluble small aggregates of Aß1-42 peptide, while no obvious alteration of plaque-associated microglia characteristics is observed. Our results support that microglial P2X4 promotes lysosomal ApoE degradation, indirectly altering Aß peptide clearance, which in turn might promotes synaptic dysfunctions and cognitive deficits. Our findings uncover a specific interplay between purinergic signaling, microglial ApoE, soluble Aß (sAß) species and cognitive deficits associated with AD.