The eATP/P2×7R Axis Drives Quantum Dot-Nanoparticle Induced Neutrophil Recruitment in the Pulmonary Microcirculation.

Exposure to nanoparticles (NPs) is frequently associated with adverse cardiovascular effects. In contrast, NPs in nanomedicine hold great promise for precise lung-specific drug delivery, especially considering the extensive pulmonary capillary network that facilitates interactions with bloodstream-suspended particles. Therefore, exact knowledge about effects of engineered NPs within the pulmonary microcirculation are instrumental for future application of this technology in patients. To unravel the real-time dynamics of intravenously delivered NPs and their effects in the pulmonary microvasculature, we employed intravital microscopy of the mouse lung. Only PEG-amine-QDs, but not carboxyl-QDs triggered rapid neutrophil recruitment in microvessels and their subsequent recruitment to the alveolar space and was linked to cellular degranulation, TNF-α, and DAMP release into the circulation, particularly eATP. Stimulation of the ATP-gated receptor P2X7R induced expression of E-selectin on microvascular endothelium thereby mediating the neutrophilic immune response. Leukocyte integrins LFA-1 and MAC-1 facilitated adhesion and decelerated neutrophil crawling on the vascular surface. In summary, this study unravels the complex cascade of neutrophil recruitment during NP-induced sterile inflammation. Thereby we demonstrate novel adverse effects for NPs in the pulmonary microcirculation and provide critical insights for optimizing NP-based drug delivery and therapeutic intervention strategies, to ensure their efficacy and safety in clinical applications.

Purinergic signaling in liver disease: calcium signaling and induction of inflammation.

Purinergic signaling regulates many metabolic functions and is implicated in liver physiology and pathophysiology. Liver functionality is modulated by ionotropic P2X and metabotropic P2Y receptors, specifically P2Y1, P2Y2, and P2Y6 subtypes, which physiologically exert their influence through calcium signaling, a key second messenger controlling glucose and fat metabolism in hepatocytes. Purinergic receptors, acting through calcium signaling, play an important role in a range of liver diseases. Ionotropic P2X receptors, such as the P2X7 subtype, and certain metabotropic P2Y receptors can induce aberrant intracellular calcium transients that impact normal hepatocyte function and initiate the activation of other liver cell types, including Kupffer and stellate cells. These P2Y- and P2X-dependent intracellular calcium increases are particularly relevant in hepatic disease states, where stellate and Kupffer cells respond with innate immune reactions to challenges, such as excess fat accumulation, chronic alcohol abuse, or infections, and can eventually lead to liver fibrosis. This review explores the consequences of excessive extracellular ATP accumulation, triggering calcium influx through P2X4 and P2X7 receptors, inflammasome activation, and programmed cell death. In addition, P2Y2 receptors contribute to hepatic steatosis and insulin resistance, while inhibiting the expression of P2Y6 receptors can alleviate alcoholic liver steatosis. Adenosine receptors may also contribute to fibrosis through extracellular matrix production by fibroblasts. Thus, pharmacological modulation of P1 and P2 receptors and downstream calcium signaling may open novel therapeutic avenues.

Astrocytic P2X7 receptor regulates depressive-like behavioral reactions of mice in response to acute stressful stimulation.

Acute stress causes depressive-like reactions in the tail suspension (TST) and forced swim tests (FST) of mice. Similarly, inescapable foot shock is able to promote the development of anhedonia as indicated by decreased sucrose consumption of treated mice in the sucrose preference test (SPT). The astrocyte-specific deletion of the P2X7R by a conditional knockout strategy or its knockdown by the intracerebroventricular (i.c.v.) delivery of an adeno-associated virus (AAV) expressing P2X7R-specific shRNA in astrocytes significantly prolonged the immobility time in TST and FST. In contrast, the shRNA-induced downregulation of the P2X7R in neurons, oligodendrocytes, or microglia had no detectable effect on the behavior of treated mice in these tests. Moreover, sucrose consumption in the SPT was not altered following inescapable foot shock treatment in any of these cell type-specific approaches. Immunohistochemistry indicated that the administered astrocyte-specific AAV efficiently conveyed expression of shRNA by hippocampal CA1 astrocytes, but not by neurons. In conclusion, P2X7R in astrocytes of this area of the brain appears to be involved in depressive-like reactions to acute stressors.

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.

The P2X7R is a crucial target for Angiotensin II-induced myocardial ferroptosis and remodeling.

Ongoing cardiac remodeling can lead to negative outcomes, such as cardiac failure and diminished myocardial function, although the remodeling process initially protects the heart as a compensatory mechanism[1] . Importantly, ferroptosis appears to be a critical process in the development of cardiac disease. In a recent publication in Redox Biology, (Zhong et al. [2] showed that reactive oxygen species (ROS) generation and cardiac ferroptosis may be the mechanisms underlying angiotensin II (Ang II)-induced cardiac remodeling, as well as that ferroptosis is required for heart impairment and cardiac dysfunction induced by Ang II. Moreover, this study provides evidence that Ang II increases the expression of P2X7 receptors (P2X7R) in cardiac tissues and that both silencing and pharmacological inhibition of P2X7R significantly inhibited Ang II-induced ferroptosis and hypertrophy. Also, this work confirmed that P2X7R deficiency mitigated the Ang II-induced deterioration of cardiac injury in mice fed an iron-rich diet. Most interestingly, this study revealed that Ang II directly interacts with the P2X7R to activate and induce nucleocytoplasmic shuttling of human antigen R (HuR), which in turn controls the stability of the mRNA of heme oxygenase 1 (HO-1) and GPX4 and subsequent ROS production, which translated to induction of myocardial ferroptosis and remodeling.

THE effect of P2X7 receptor activation on functional responses of human left internal mammary artery.

The Purinoreceptor 7 (P2X7R) has become a promising drug target in many cardiovascular diseases, including coronary artery disease, since prolonged activation of P2X7R could promote vascular dysfunction, atherosclerosis, and thrombosis. Thus, we aimed to study the effects of P2X7R activation on vascular relaxation responses of the human left internal mammary artery (LIMA). Sections of redundant human LIMA were cut into 3-mm wide rings,, suspended in 20-mL organ baths containing physiologic salt solution, and attached to an isometric force transducer connected to a computer-based data acquisition system. Long-term (60 min) incubation with specific P2X7R agonist Bz-ATP caused significant reductions in relaxation responses of LIMA to ATP and acetylcholine, which were reversed by selective P2X7R antagonists Brilliant Blue G or AZ11645373, whereas there were no changes in relaxation responses to endothelium-independent vasodilators isoprenaline, cAMP analog 8-Br-cAMP, and nitric oxide donor sodium nitroprusside. The impairment in relaxant responses of LIMA to endothelium-dependent vasodilators following activation of P2X7R for the long-term may contribute to postoperative LIMA vasospasm and hypertension. Modulation of P2X7R activity with selective agents may represent a new potential therapeutic approach in patients undergoing coronary artery bypass grafting surgery.

Activation of P2X7R Inhibits Proliferation and Promotes the Migration and Differentiation of Schwann Cells.

In the vertebrate nervous system, myelination of nerve fibers is crucial for the rapid propagation of action potentials through saltatory conduction. Schwann cells-the main glial cells and myelinating cells of the peripheral nervous system-play a crucial role in myelination. Following injury during the repair of peripheral nerve injuries, a significant amount of ATP is secreted. This ATP release acts to trigger the dedifferentiation of myelinating Schwann cells into repair cells, an essential step for axon regeneration. Subsequently, to restore nerve function, these repair cells undergo redifferentiate into myelinating Schwann cells. Except for P2X4R, purine receptors such as P2X7R also play a significant role in this process. In the current study, decreased expression of P2X7R was observed after sciatic nerve injury, followed by a gradual increase to the normal level of P2X7R expression. In vivo experiments showed that the activation of P2X7R using an agonist injection promoted remyelination, while the antagonists hindered remyelination. Further, in vitro experiments supported these findings and demonstrated that P2X7R activation inhibited the proliferation of Schwann cells, but it promoted the migration and differentiation of the Schwann cells. Remyelination is a prominent feature of the nerve regeneration. In the current study, it was proposed that the manipulation of P2X7R expression in Schwann cells after nerve injury could be effective in facilitating nerve remyelination.

Astrocytic P2X7 receptor in retrosplenial cortex drives electroacupuncture analgesia.

P2X7 receptor (P2X7R) has been found to contribute to the peripheral mechanism of acupuncture analgesia (AA). However, whether it plays an important role in central mechanism remains unknown. In this study, we aimed to reveal the role of astrocytic P2X7R in retrosplenial cortex (RSC) in AA and provide new evidence for underlying the central mechanism of AA. We applied the chemogenetic receptors hM3Dq to stimulate or hM4Di to inhibit astrocytes ligand clozapine-N-oxide (CNO) following injection of adeno-associated virus (AAV) into the bilateral RSC, or pharmacologically intervened in the activity of the purinergic receptor P2X7R. Current data indicated that chemogenetic inhibition of astrocytes or injection of P2X7R agonist Bz-ATP in the bilateral RSC significantly reverses the analgesic effect of electroacupuncture (EA) in formalin tests while the bilateral injection of the P2X7R antagonist A438079 alleviated formalin-induced nociceptive behavior. Additionally, chemogenetic suppression of astrocytic P2X7R by injection of AAV in the bilateral RSC decreased hind paw flinches induced by formalin in the mice. These findings indicate the participation of both astrocytes and P2X7R in the RSC in EA analgesic. Moreover, P2X7R on astrocytes in the RSC appears to play a critical role in the ability of EA to attenuate formalin-induced pain responses in mice.

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.

Moxibustion pre-treatment attenuates seizure severity during status epilepticus and counteracts the proconvulsant function of the purinergic P2X7 receptor.

Moxibustion, traditional Chinese medicine treatment, involves the warming of specific acupuncture points of the body using ignited herbal materials. Evidence suggests beneficial effects of moxibustion in several brain diseases including epilepsy, however, whether moxibustion pretreatment impacts on seizures and what are the underlying mechanisms remains to be established. Evidence has suggested the purinergic ATP-gated P2X7 receptor (P2X7R) to be involved in the actions of moxibustion. Moreover, P2X7R signalling is now well established to contribute to long-lasting brain hyperexcitability underlying epilepsy development. Whether P2X7R signalling is involved in the seizure-reducing actions of moxibustion has not been investigated to date. For our studies we used C57BL/6 male mice that received moxibustion pre-treatments at the acupoints Zusanli (ST36) and Dazhui (GV14) once daily for either 7, 14, or 21 days. This was followed by an intraperitoneal injection of kainic acid (KA, 30 mg/kg) to induce status epilepticus. Behavioral changes during KA-induced status epilepticus were analyzed according to the Racine scale. Changes in electrographic seizures were analyzed via cortical implanted electroencephalogram (EEG) electrodes. While no effect on seizure severity was observed following 7 days of moxibustion pre-treatment, moxibustion pre-treatment at both ST36 and GV14 for 14 or 21 days significantly reduced KA-induced behavior seizures at a similar rate. Cortical EEG recordings showed that 14 days of moxibustion pre-treatments also reduced electrographic seizures, confirming the anticonvulsant actions of moxibustion pre-treatment. To determine whether moxibustion impacts the pro-convulsant actions of P2X7R signaling, mice were treated with the P2X7R agonist BzATP or P2X7R antagonist A438079. While treatment with the P2X7R agonist BzATP exacerbated seizure severity, treatment with the P2X7R antagonist reduced seizure severity. We further found that moxibustion pre-treatment attenuated epileptic seizures by counteracting the effects of BzATP. These results suggest that moxibustion pre-treatment at the acupoints ST36 and GV14 for 14 days has anti-epileptic effects, which may counteract the proconvulsant functions of the P2X7R.