Pharmacological evidence for the stimulation of NADPH oxidase by P2X7 receptors in mouse submandibular glands

ATP in the 100 μM-1 mM concentration range provoked a calcium-independent increase of the oxidation of dichlorodihydrofluorescein (DCFH) to dichlorofluorescein (DCF) by mouse submandibular cells. 3′-O-(4-benzoyl)benzoyl adenosine 5′-triphosphate (BzATP), a P2X7 agonist, but not a muscarinic or an adrenergic agonist, reproduced the effect of ATP. The inhibition of phospholipase C by U73122 or the potentiation of P2X4 receptor activation with ivermectin did not modify the response to ATP. ATP did not increase the oxidation of DCFH in cells isolated from submandibular glands of P2X7 knockout mice or in cells pretreated with a P2X7 antagonist. The inhibition of protein kinase C or of mitogen-activated protein kinase (MAP kinase) or of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase blocked the oxidation of DCFH without affecting the increase of the intracellular concentration of calcium or the uptake of ethidium bromide in response to extracellular ATP. From these results it is concluded that the activation of the P2X7 receptors from submandibular glands triggers an intracellular signalling cascade involving protein kinase C and MAP kinase leading to the stimulation of NADPH oxidase and the subsequent generation of reactive oxygen species

Connection between mitochondrial inner membrane depolarization and reactive oxygen species generation caused by P2X7 receptor activation in submandibular gland cells.

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P2X7 receptor activation causes mitochondrial membrane depolarization through sodium influx in submandibular glands.

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Implication of different ion transport systems in the P2X7 receptor mediated mitochondrial membrane depolarization in submandibular gland cells

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Heterogeneous distribution of P2X7 receptors on the plasma membrane of rat submandibular glands. Implications in cellular signaling pathways.

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Study of the responses coupled to P2X4 receptor activation in mouse peritoneal macrophages. Ligand-gated ion channels,

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Are cathelin-derived peptides natural agonists of P2X7 receptors? .

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The calcium run-down observed in P2X7 receptor signalling is mediated by a tyrosine phosphatase in peritoneal macrophages.

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Stimulation by P2X7 receptors of calcium-dependent production of reactive oxygen species (ROS) in rat submandibular glands.

BACKGROUND: Agonists of P2X₇ receptors increase the production of reactive oxygen species (ROS) in immunocytes. In this work we tested this response and its effect on mitochondrial inner membrane potential (Deltapsi(m)) in exocrine glands. METHODS: The production of ROS by rat submandibular glands was investigated by measuring the oxidation of dichlorodihydrofluorescein (DCFH), a fluorescent probe. The Deltapsi(m) was estimated with tetramethylrhodamine. RESULTS: Activation of P2X₇ receptors by ATP or Bz-ATP increased the production of ROS. This response was not modified by inhibitors of phospholipase A2 or of various kinases. The effect of ATP was calcium-dependent and was blocked by diphenyliodonium, an inhibitor of flavoproteins. It was not affected by rotenone, an inhibitor of the complex I of the mitochondrial electron transfer chain. Scavengers of ROS had no effect on the dissipation of Deltaψ(m) by ATP. CONCLUSIONS: We conclude that, in rat submandibular glands, P2X₇ receptors stimulate in a calcium-dependent manner an oxidase generating ROS, suggesting the involvement of the dual oxidase Duox2. The production of ROS does not contribute to the depolarization of mitochondria by purinergic agonists. GENERAL SIGNIFICANCE: Purinergic receptors could be regulators of the bactericidal properties of saliva by promoting both the secretion of peroxidase from acinar cells and by activating Duox2.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

The secretion of IL-1β in response to extracellular ATP: do only P2X7 receptors matter? .

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