Fcis an element of RI Signaling of Mast Cells Activates Intracellular Production of Hydrogen Peroxide:Role in the Regulation of Calcium Signals.

摘要

Earlier studies,including our own,rvealed that activation of mast cells is accompanied by production of reactive oxygen species (ROS) that help to mediate the release of the inflammatory mediators,including histamine and eicosanoids.However,little is known about the mechanisms of ROS production,including the species of oxidants produced.In this study we show that in both the RBL-2H3 mast cell line and bone marrow-derived mast cells,Fcis an element ofRI cross-linking stimulates intracellular oxidative burst,including hydrogen peroxide (H_2O_2) production,as defined with the oxidant -sensitive dyes dichlorofluorescein and scopoletin and the selectiv escavenger ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one).Th eoxidative burst was observed immediately after stiulation and was most likely due to an NAD(P)H oxidase.Experiments using selective pharmacological inhibitors demonstrated that activation of tyrosine kinases and phosphatidylinositol-3-kinase is required for induction of the oxidative burst.Blockade of the oxidative burst by diphenyleneiodonium impaired the release of preformed granular mediators,such as histamine and beta-hexosaminidase,and the secretion of newly synthesized leukotriene C_4,whereas selective scavenging H_2O_2 by ebselen impaired leukotriene C_4 secretion,but not degranulation.Sustained elevation of cytosolic calcium through store-operated calcium entry was totally abolished when ROS production was bolcked.In contrast,selective depletion of H_2O_2 caused a considerable decrease and delay of the calcium response.Finally,tyrosine hosphorylation of phospholipase Cgamma and the linker for activation of T cells,an event required for calcium influx,was suppressed by diphenyleneiodonium and ebselen.these studies demonstrate that activation fo te intracellular oxidative burst is an important regulatory mechanism of mast cell responses.