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The interaction of lipopolysaccharide-primed murine peritoneal macrophages with ivermectin, an antiparasite drug which potentiates P2X(4) receptors and dynasore which inhibits the GTPase activity of dynamin, a protein contributing to the internalization of plasma membrane proteins, was tested. Murine peritoneal macrophages express P2X(4) receptors which are mostly intracellular. In cells from P2X(7)-knockout mice (KO mice), 10 µm adenosine triphosphate (ATP) provoked a transient increase of the intracellular concentration of calcium. Ivermectin had no effect by itself but potentiated the increase of the intracellular concentration of calcium by ATP. The combination of ATP plus ivermectin also decreased the intracellular concentration of potassium and promoted the secretion of IL-1β. Concentrations of dynasore above 50 µm affected the integrity of mitochondria (MTT test) and of the plasma membrane (release of lactate dehydrogenase, LDH). At a 10 µm concentration, dynasore had no effect on the responses to ATP and on the internalization of P2X(4) receptors. By itself dynasore promoted the release of potassium and the secretion of IL-1β after activation of caspase-1. In conclusion, our results confirm that ivermectin potentiates the responses coupled to P2X(4) receptors probably by interaction with an allosteric site. We also show that this potentiation triggers the release of IL-1β by macrophages. As opposed to ivermectin, dynasore has no effect on P2X(4) receptors. This drug triggers a potassium efflux via a mechanism which does not involve purinergic receptors and generates, in consequence, the activation of caspase-1 and the secretion of IL-1β.

The regulation of interleukin (IL)-1 expression and secretion by salivary glands and macrophages in response to lipopolysaccharides (LPS) was compared. In wild-type mice, injection of LPS significantly decreased the volume of saliva stimulated by pilocarpine and increased its protein and amylase concentration. It did not modify the salivary concentration of IL-1β. The cytokine was expressed by submandibular acini and ducts. Macrophages also expressed IL-1β but at lower concentration than salivary glands. The pre-incubation of macrophages with LPS increased the phosphorylation of IκB and the expression of IL-1β. Adenosine triphosphate also promoted the secretion of the cytokine by these cells. These responses were absent in submandibular gland cells. These glands expressed CD14, TLR4 and MyD88. P2X(7)-KO mice secreted a lower volume of saliva which contained less proteins and amylase. In conclusion, IL-1β is constitutively expressed by submandibular glands and its secretion is not regulated by a P2X(7) agonist. In these cells, LPS do not activate the nuclear factor-κB-pro-IL-1β axis in spite of the expression of the proteins involved in their recognition.