Kinetics and mechanism of ATP-dependent IL-1 beta release from microglial cells.
Endotoxin-dependent release of IL-1 beta from mouse microglial cells is a very inefficient process, as it is slow and leads to accumulation of a modest amount of extracellular cytokine. Furthermore, secreted IL-1 beta is mostly in the procytokine unprocessed form. Addition of extracellular ATP to LPS-primed microglia caused a burst of release of a large amount of processed IL-1 beta. ATP had no effect on the accumulation of intracellular pro-IL-1 beta in the absence of LPS. In LPS-treated cells, ATP slightly increased the synthesis of pro-IL-1 beta. Optimal ATP concentration for IL-1 beta secretion was between 3 and 5 mM, but significant release could be observed at concentrations as low as 1 mM. At all ATP concentrations IL-1 beta release could be inhibited by increasing the extracellular K+ concentration. ATP-dependent IL-1 beta release was also inhibited by 90 and 60% by the caspase inhibitors YVAD and DEVD, respectively. Accordingly, in ATP-stimulated microglia, the p20 proteolytic fragment derived from activation of the IL-1-beta-converting enzyme could be detected by immunoblot analysis. These experiments show that in mouse microglial cells extracellular ATP triggers fast maturation and release of intracellularly accumulated IL-beta by activating the IL-1-beta-converting enzyme/caspase 1.
Sanz
J M
JM
Department of Experimental and Diagnostic Medicine, Section of General Pathology, and Center of Biotechnology, University of Ferrara, Ferrara, Italy.
Di Virgilio
F
F
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D020170:Caspase 1 / Q000378:metabolism; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D004306:Dose-Response Relationship, Immunologic; D004789:Enzyme Activation / Q000276:immunology; D007375:Interleukin-1 / Q000378:metabolism*; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D017628:Microglia / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D008970:Molecular Weight; D011188:Potassium / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D058486:Receptors, Purinergic P2X7
D007375:Interleukin-1; D008070:Lipopolysaccharides; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate; D020170:Caspase 1; D011188:Potassium